For example, green and yellow are colors of confusion in red-green CVD, but it is very common to mix forest green (█) with bright yellow (█). Mistakes by the colorblind increase drastically when uncommon shades are used, e.g. neon green (█) with dark yellow (█). For denotative tasks, using colors that are classically associated with a color name. For example, dont use burgundy (█) to represent "red". Unordered Information
A common task for designers is to select a subset of colors (qualitative colormap) that are as mutually differentiable as possible (salient). For example, player pieces in a board game should be as different as possible. Classic advice suggests using Brewer palettes, but several of these are not actually colorblind-accessible. A recent, free, powerful tool that checks color contrast of a group of colors is Adobes Color Blind Safe Tool. Unfortunately, the colors with the greatest contrast to the red-green colorblind tend to be colors of confusion to the blue-yellow colorblind, and vice versa. However, since red-green is much more prevalent than blue-yellow CVD, design should generally prioritize those users (Deutans, then Protans). Ordered Information
A common task for data visualization is to represent a color scale, or sequential colormap, often in the form of a heat map or choropleth. Several scales are designed with special consideration for the colorblind and are widespread in academia, including Cividis, Viridis and Parula (Matlab). These comprise a light-to-dark scale superimposed on a yellow-to-blue scale, making them monotonic and perceptually uniform to all forms of color vision.
However, there is a claim that there is no firm evidence that color deficiency did cause the collision, or that it might have not been the sole cause.In 1920, Frederick William Edridge-Green devised an alternative theory of color vision and color blindness based on Newtons classification of 7 fundamental colors (ROYGBIV). Edridge-Green classified color vision based on how many distinct colors a subject could see in the spectrum. Normal subjects were termed hexachromic as they could not discern Indigo. Subjects with superior color vision, who could discern indigo, where heptachromic. The colorblind were therefore dichromic (equivalent to dichromacy) or tri-, tetra- or pentachromic (anomalous trichromacy). Society and culture
Design implications
Color codes are useful tools for designers to convey information. The interpretation of this information requires users to perform a variety of Color Tasks, usually comparative but also sometimes connotative or denotative. However, these tasks are often problematic for the colorblind when design of the color code has not followed best practices for accessibility. For example, one of the most ubiquitous connotative color codes is the "red means bad and green means good" or similar systems, based on the classic signal light colors. However, this color coding will almost always be undifferentiable to either (Deutans or Protans) and therefore should be avoided or supplemented with a parallel connotative system (symbols, smileys, etc.). Good practices to ensure design is accessible to the colorblind, include:

When possible (e.g. in simple video games or apps), allowing the user to choose their own colors is the most inclusive design practice.