How to remove elliptical color bands on textures

So we try to creat an Escape Room. One Riddle is that u have to get the 3 numbers of a specific RGB Color. The Problem is that no matter how many lights I disable or add, there are always these weird Ellipses.

That means in this picture are like 5 different colors.

I already created a new layer for the picture and disabled all lightnings. Its hard to see in this picture but if you zoom really close u can see it.

191242-screenshot-2022-01-16-014427.gif

This is called color banding.

Color banding on textures (i.e. without lighting) comes from source image or texture color-space compression (more likely but not always).

simpleton’s answer:

Color-space compression (less colors) makes significant practical sense because it makes texture files take less space. But if you have one-off special texture that is gameplay-critical then just disable compression on this specific texture asset and it’s done.

chad tech artist’s answer:

Switch from 8-bit per channel to 16 or 32 per color channel compression for this texture asset.