Design Principles

Don't use more than (about) six colors

• Using color categories that are relatively universal makes it easier to see differences between colors.

The more colors you need (that is, the more categories you try to visualize at once), the harder it is to do this.

• But different colors should be used for different categories (e.g., male/female, types of fruit), not different values in a range (e.g., age, temperature).

• So, no rainbows! We often think that the order of colors in our "rainbow" is easy for everyone to understand, but this order is not universal and will make charts and maps harder to read.

If you want color to show a numerical value, use a range that goes from white to a highly saturated color in one of the universal color categories.

• And remember, some people have color blindness.

Use Vischeck to test your images.

• Also, print out your charts to test what it looks like in gray scale. (For grayscale to work, you need to vary both hue and saturation).