Apply category logic to best practices image color

[arouault]

Use the best practices category logic to assign a color to each image based on its category https://docs.google.com/spreadsheets/d/1n4kxUXxX3e1qgDIJdUUuiSvv8kvMjUMupeXT5q2QMG0/edit?usp=sharing

[ericyoungberg]

This isn't a thing anymore