I don’t know if things have changed since I left, but that would most likely be the kind of modification that makes them unserviceable.
If I'm remembering the iFixit videos right, slapping some color on these is the least of the issues regarding repairability, at least from a practical sense... Talking "0 out of 10" score. If you have a warranty or AC+ issue, the bud is flat out getting replaced. When it comes to Apple policy on modifications, maybe it's a deal-breaker right off the bat. Who knows.