He says in the video you can use the art kit as creatively as you wish so "trail renders, shaders, particle effects" are all good. You could write a pretty simple shader to change the colours then by that definition.
I wasn't sure about this either but it also says "cropping, tinting, etc.". Recoloring is very similar to tinting so I think it's no problem, you don't have to go through the effort to create an extra shader I don't think. Correct me if I am wrong mods
