Label colors and label interpolator

[kephale]

@uermel suggested:

• change label colors so they are more distinct and better suited for cryoEM data
• use Lorenzo's label interpolator

[kephale]

Label colors were implemented in 884bfe7

[kephale]

@uermel I'm up for using https://github.com/brisvag/napari-label-interpolator but it isn't 100% clear to me how it would be used. I can imagine using the interpolator to paint additional pixels between some existing painted regions of the same label, is that what you were thinking about (e.g. paint the top, middle, and bottom of a ribosome, then fill in the rest)? It looks like we might need to paint per-instance to get this to work as intended.

[uermel]

Yes, that's what I meant, but mainly for the membrane case. It's more tedious to trace long sections of membrane on each slice than to pick particles with the 3D sphere paint tool.

[kephale]

@uermel also wanted to change individual colors. There is a related napari zulip thread that is active right now: https://napari.zulipchat.com/#narrow/stream/212875-general/topic/Changing.20a.20single.20label.20color.20in.20a.20.60DirectLabelColormap.60