The usual consensus as far as cosmetic color and warranty compatibility is that so long as you use plastidip (and peel it off before sending it in), it doesn't harm thermal performance much, and it should still be able to be claimed as under warranty. Mind you, I'm not aware of a case where someone has sent in a painted part and gotten a response either way, nor of a case where a plastidipped part was sent in with the dip peeled off. So, you have an avenue to explore, but no definitive way to go.
Also, I'd personally run the hardware unmodded for a few weeks/months, to get it out of the bathtub curve and burned in, so any major problems present themselves before the mods occur, since even if they will replace it, you are then out the modding effort, which can be substantial.
Best of luck
Xeno
