Add basic coloring

[BKE]

Still, what I miss most from an earlier version. It was so fast to work with! No round-robin with endless trials.

Please separate the color function out of visualization

The visualization function drops the FPS significantly on my M1 iPad pro and M1 imac, and all the line borders are disappeared, it makes me quite painful when colorizing my models and especially for the tiny parts and complex shapes. Please makes the color function stand-alone like it was before.