How to remove the weird rainbow-like pattern?

[leviathanimation]

I am making an animation for my visual novel using anime studio. When I render the images, everything seems fine, but once the video is done being publish, these weird pattern appear and I don't know what is causing them. Anyone here who knows how to fix this? I think it's just a color problem based on certain settings but I don't know what it is called or where to even look.

[SundownKid]

That appears to be compression from your video format. You will basically need to increase the quality of whatever video you're outputting to avoid that.

[Imperf3kt]

The technical name for that is called banding and it is caused by converting a 24bit png into an 8bit YUV 4:2:0 file

The only way to avoid it (its a flaw in how video works) is to either increase the bit-depth or dither.
10bit is reasonable, 12bit is a good compromise, but you should aim for 16 or the original 24.
The problem here, is that you cannot use 16bit or higher video as it currently does not exist and 10 or 12 bit require specialised decoders which Ren'Py lacks. So you're stuck with 8bit (or less) to encode your video as.

So increased bit-depth is out, what about dithering?
Dithering is going to increase the bandwidth a lot and if you do it too much, it becomes noticeable, not to mention increasing the filesize and minimum requirements to play it back.
Dither is effectively noise. Avoid ordered dithering, this method is too easily noticed and can be distracting.