By calling attention to the perception of data graphics among color-impaired readers, we hoped to raise awareness of an even more prevalent phenomenon: the misuse of spectral, or “rainbow,” color schemes. David B. Stephenson is quite right regarding the incidence of different forms of color-vision impairment, which varies among racial and ethnic groups and is much lower for females [Sharpe et al., 1999]. Our article highlighted simulations of the less common protanopia to dramatize the general peril of spectral schemes.
Figure 1 shows simulations of spectral, diverging, and progressive color schemes as they might appear to readers with either of the most common forms of color deficiency Figures 1a and 1b illustrate why the adage “red and green should never be seen” is a good one. The simulations in the right-hand column show how deuteranopes may find it difficult or impossible to distinguish between red and green.