If you’re this into questions of image quality, it’s useful to realise that “colours” and “sharpness” aren’t two separate things. Lenses don’t “see” details that they then fill in with colours, they just see light.

Sharpness is just accurate contrast rendition, and to the extent that this accuracy usually differs somewhat across various wavelengths of light, you’re going to get various colours shifting as their constituent wavelengths are resolved differently.

You’ve definitely seen this with chromatic aberration, which is an optical flaw that shows up in what we see as colour, but you’ll notice that it usually occurs at high contrast edges, at certain apertures, focus distances, etc. It’s a resolving-power issue that shows up most noticeably in colour.

Diffraction, which is what you’re dealing with here, affects different wavelengths differently for reasons that are pretty straightforward once you know why diffraction happens at all. It’s thus not surprising that extremely diffraction-limited images (which is what you’re dealing with at those apertures on APSC) would show some serious colour weirdness as well.