Make material color id generation more predictable

[and-rad]

When material ids are baked to a texture, the colors are selected randomly. This is not ideal because the texture is meant to be used as a mask in material setups. The random nature of the color creation means that these colors will be different with each new bake and any material that uses them will have to be adjusted.

A solution to this problem needs to retain colors for each material either based on the material's index or name.