Traditionally, red is used to indicate problematic or dangerous values. This is backed up by a long cultural history, at least in the Western cultural context, that associates red with danger.
I'd say this fact alone makes the color red extremely important in data visualization. The current trend of "but some people can't see red, so let's just use yellow and blue everywhere" seems utterly inadequate for addressing both the importance of red and the problem of color blindness.
Traditionally, red is used to indicate problematic or dangerous values. This is backed up by a long cultural history, at least in the Western cultural context, that associates red with danger.
I'd say this fact alone makes the color red extremely important in data visualization. The current trend of "but some people can't see red, so let's just use yellow and blue everywhere" seems utterly inadequate for addressing both the importance of red and the problem of color blindness.