Guideline: Don’t use more than 6 colours together*
I’m trying to differentiate different file types in a tree map and a color mapping seems to be the most popular way in doing so. However, with about 10-12 file types in my tree map, the use of color is problematic, as according to the guideline I shouldn’t use more than 6 (and also have to avoid using color combinations that are difficult to distinguish for the color blind). Is color therefore completely discouraged and what would be appropriate visual mappings for categorical data in tree maps instead? Is combining colors with other methods, like textures a possiblity?