Many visualisations use colours to represent data values, either to show quantitative scales or categorical classifications. One of the most common colour metaphors used in visual displays involves the use of a red-green colour scheme, sometimes known as “RAG” or “traffic light” colours. These colours are used to convey notions of green = ‘good’ or ‘above average’ and red = ‘bad’ or ‘below average’ in some cultures, and the reverse in others. Such colour connotations are long-established and widely used, especially in financial or corporate contexts, but whilst they provide a certain immediacy in their meaning for many viewers, around 4.5% of the population are colour-blind (8% of men) with the red-green colour deficiency “Deuteranopia” being the most common form. This means a significant proportion of viewers may not be able to perceive important such visual encodings.
I’m not the biggest fan of some of them, but there are some really good ideas in here.