Accommodating color vision deficiencies in biomedical publications

Abstract

Color vision deficiencies, especially red-green types such as deuteranomaly and protanopia, affect many individuals, particularly men, and pose challenges in fields that rely on color-coded visualizations. In biomedical journals, figures such as heatmaps and fluorescence images often use red-green color contrasts that are inaccessible to readers with color vision deficiencies, leading to misinterpretation and reduced clarity. Studies show that a large proportion of scientific figures remain problematic, underscoring the need for inclusive design. This review outlines strategies to improve figure accessibility, including avoiding red-green combinations, adopting perceptually uniform palettes, ensuring luminance contrast, and supplementing colors with patterns or annotations. Providing alternative text and testing figures with color-blindness simulators further enhances usability. Incorporating these practices promotes equitable access to scientific knowledge and strengthens the clarity and impact of published research in biomedical journals and textbooks.

Introduction

Color discrimination deficits are common and affect many people. These challenges affect fields such as biology and medicine, where color-coded visuals are widespread [1]. In biomedical journals, which often use heatmaps, color-coded graphs, and fluorescent images, it is essential to accommodate readers with color vision disorders to ensure accurate interpretation and communication. This review highlights the importance of deliberate selection of figure color schemes and offers guidance for optimizing visual design in biomedical publications, focusing on the Anatomy & Cell Biology journal and red-green color vision impairment, the most prevalent deficit.

Color Vision Deficiencies

Color vision deficiencies (CVDs), often referred to as color blindness, are inherited visual disorders that impair the ability to discriminate between specific colors [1]. The most common form of CVD is red-green, which can be further classified into protanopia (reduced sensitivity to red light) and deuteranomaly (reduced sensitivity to green light) (Fig. 1) [1, 2]. The varying degrees of severity in protanopia and deuteranopia further complicate visual discrimination for affected individuals [1]. Globally, deuteranomaly is recognized as the most prevalent form of CVD, a pattern likewise observed in the Korean population [3]. These conditions arise from alterations in genes encoding photoreceptor proteins on the X chromosome [4]. Additionally, there are less common forms, such as blue-yellow deficiencies and complete color blindness (achromatopsia) [5].

Fig. 1.

The most prevalent color vision deficiency is red-green deficiency, with subtypes: (A) deuteranomaly (greens muted/reddish), (B) protanomaly (reds dim/grayish), (C) deuteranopia (loss of green cones; blue/gold vision, poor red/green/yellow distinction), and (D) protanopia (loss of red cones; reds dark/black, colors shift toward blue/gold).

CVDs are more common in males, affecting about 1 in 12, whereas only about 1 in 200 females are affected [4]. The impact can be substantial. Affected individuals face challenges in daily activities and in academic and professional pursuits [4]. This may make many standard color palettes inaccessible. A population-based study of 4,941 Korean adults reported a 2.9% prevalence of CVD from 2014–2015. Rates were much higher in males (5.6%) than in females (0.2%) [3].

Color-Coded Figures in Scientific Journals

Color coding is now common in scientific journal articles, driven by digital screens and increased color printing [5]. Biomedical journals often use color-coded graphs and heat maps to communicate key information. However, graph design often fails to account for CVDs, even as more journals recognize the need for accessibility [6]. For instance, people with deuteranomaly cannot easily distinguish the typical red and green hues in heat maps (Fig. 2), which are popular in gene expression studies [7], including those in Anatomy & Cell Biology [8]. Fluorescence imaging, a staple in cell biology, also presents accessibility issues when the red-green color contrast is added (Fig. 3).

Fig. 2.

(A) Standard red/green heatmaps clearly separate high (red) and low (green) gene expression under normal vision. (B, C) For individuals with deuteranopia or protanopia, however, the red/green contrast collapses into yellow-brown tones, obscuring differential patterns.

Fig. 3.

(A) An immunofluorescent image using blue (nucleus), red (actin), and green (microtubules) clearly separates cytoskeletal components under normal vision. (B, C) In deuteranopia or protanopia, however, red and green signals merge into yellow-brown tones, obscuring the distinction between actin filaments and microtubules. As a result, essential information regarding structural relationships is no longer discernible.

Three-dimensional shape and volumetric comparison analyses are widely used in areas such as traditional gross anatomy and forensic medicine. They are also important in plastic and aesthetic surgery to evaluate morphological differences by age, sex, and ethnicity [9]. Rainbow-scale color maps often visualize these variations. However, this approach can be problematic for those with red-green CVDs. The chosen palette may obscure critical distinctions (Fig. 4).

Fig. 4.

Simulated midfacial skeletal models with heatmaps illustrating male–female skull differences across age groups. Red areas indicate regions of protrusion, whereas blue denotes recession. Compared with normal vision (A), readers with red-green color vision deficiency (B, C) perceive rainbow and red/yellow/blue scales as less distinct, resulting in blurred protrusion-recession boundaries and reduced intensity discrimination.

Studies

The reduced visual discernibility of conventional red-green color schemes in scientific figures means that many readers may struggle to interpret them accurately [10]. This limitation increases the risk of misinterpreting critical data patterns and ultimately hinders effective knowledge transfer [11]. Several studies have examined the use of color in scientific journals, highlighting how certain schemes may obscure interpretation for readers with CVDs. A study examining 580 papers in the biological sciences found that roughly half of the figures were partially or entirely inaccessible to readers with red-green CVDs [5]. Stevens et al. [12] analyzed 66,253 images from Elife journal articles and found that 85.6% contained at least one color combination that could pose challenges for individuals with moderate-to-severe deuteranomalous color vision. A recent study by Stoelzle and Stein [13] further revealed that approximately 47% of publications in Hydrology and Earth System Sciences journal in 2020 utilized visualizations that were neither scientifically correct, perceptually uniform, nor friendly to readers with CVDs. These studies highlight the extensive scope of the problem in the scientific literature, underscoring the urgent need for biomedical journals to establish publication policies that ensure accessibility for readers with CVDs.

Accommodating Red-Green Color Vision Deficiencies in Biomedical Journal Figures

The adoption of perceptually distinct color schemes for individuals with deuteranomaly and other CVDs is essential to enhance the accessibility and clarity of scientific figures in biomedical journals; however, current initiatives remain inadequate. Some journals have taken steps to improve the accessibility of scientific figures for readers with impaired color discrimination, highlighting the importance of considering CVDs in figure design for scientific publications. One notable example comes from the Nature portfolio. Nature and its affiliated publications have established editorial and publication guidelines to maximize the accessibility of illustrations for readers with color vision impairment [14]. The Journal of Physiology and Experimental Physiology mandates that information must not be conveyed solely through color. Authors are instructed to employ accessible combinations such as green-magenta or yellow-blue, or to use grayscale for multichannel images [15]. The American Society for Cell Biology also provides formal guidance, integrated into its publication standards, for accessible scientific figures [16]. ACS Publications recently highlighted the importance of accessibility in figures by incorporating patterns, textures, and alt-text in addition to CVD–friendly palettes [17].

To enhance accessibility for readers with red-green CVDs, the author suggests that the Anatomy & Cell Biology journal also adopt inclusive figure design strategies. Effective approaches may include:

1. Avoid problematic color combinations, especially red and green: instead of relying on red-green color schemes, choose sequential or diverging color palettes that avoid them. For example, avoid red-green combinations in figures and instead use color schemes with easily distinguishable colors, such as blue and yellow. Alternative palettes suited for individuals with red-green CVDs include combinations like red and blue, purple and green, green and magenta, or red and cyan (Fig. 5). A more accessible approach is to limit the use of multiple colors to only when it is strictly necessary. Often, data can be effectively conveyed using black and white, grayscale, or a single-color scale, eliminating the need for two colors solely for aesthetic purposes.

Fig. 5.

Accessible color palettes for heatmap visualization. Standard green-red scales fail for ≈8% of the male population with red-green color vision deficiency (CVD). Alternative palettes such as green-magenta, cyan-red, light blue-yellow, purple-orange, and blue-red provide stronger perceptual contrast by leveraging distinct spectral separation, thereby improving interpretability for readers with color vision deficiencies.

2. Use ready-made color palettes suitable for CVDs: try options like Colorbrewer or the Viridis scale (Fig. 6), as these are designed to be perceptually uniform and easy to distinguish for those with impaired color discrimination.

Fig. 6.

The Viridis scale offers a perceptually uniform and color vision deficiency (CVD)–friendly alternative to traditional red-green palettes by emphasizing luminance and blue-yellow contrasts. For example, in facial temperature heatmaps, it enables clear separation of low (purple/blue), mid (green), and high (yellow/bright green) values, ensuring data integrity for readers with difficulty distinguishing red and green hues.

3. Include luminance differences: ensure that figure colors exhibit adequate luminance contrast, enabling readers with CVDs to reliably differentiate visual elements (Fig. 7).

Fig. 7.

Effective graph design for color vision deficiency (CVD) requires luminance contrast. (A) Relying solely on color differences, especially red and green of similar brightness, renders elements indistinguishable for individuals with red-green CVD. (B) Introducing a significant luminance difference ensures elements remain distinct, regardless of color perception, improving accessibility for all readers.

4. Add patterns and symbols with color: enhance color-coded visualizations by incorporating supplementary cues—such as patterns, textures, or annotations—to improve the differentiation of elements and facilitate interpretation for populations with color perception deficits (Fig. 8).

Fig. 8.

Comparison of ineffective and effective graph-design strategies for readers with color vision deficiencies (CVD). Relative to solid red-green comparison bar graphs (A), the improved design (B) incorporates redundant visual cues—such as patterns and symbols—beyond color hue to enhance data clarity and accessibility.

5. Provide alternative text descriptions: including alternative text descriptions for color-coded figures ensures that readers with CVDs can effectively access, perceive, and interpret the information conveyed by visual elements.

6. Validate figures with CVD simulation tools: when creating visualizations, it is recommended to verify that the chosen color palette remains accessible to users with CVD using online simulators. For instance, the Coblis — Color Blindness Simulator [18] allows users to preview how images appear under different types of CVD.

Conclusion

To enhance clarity and inclusiveness in scientific communication, it is recommended that biomedical journals adopt policies encouraging the use of perceptually uniform color schemes that remain accessible to all readers, including those with color discrimination difficulties. Considering the needs of individuals with CVD is important for the accurate dissemination of research findings. Employing color palettes that are interpretable to these readers supports the broader objectives of scientific publishing—equity, inclusivity, and universal access to knowledge—while reducing the risk of misinterpretation arising from avoidable design choices.