As Almar suggested here we can just migrate to pygfx.cm.create_colormap(). This will make things easier and let us use custom colormaps with whatever number of custom colors. This is necessary for @KceniaB usecase with the probability heatmaps.

Can create a TextureMap like this with using the cmap library to generate the cmap array as well:

texture_map = gfx.cm.create_colormap(cmap.Colormap(["r", "cyan", "magenta"]).lut(3), n=3)

Can then just set this on material.map for images, and texcoords for geometries (lines, scatters, meshes).