The new color cover is still an OEM part (at least the one I bought was).
But really a moot issue because you can always swap back the original shell before sending it in for repair. DJI can't tell the color of your done from the flight log.
When I removed mine recently, I realised two of the screws had their heads sealed with glue, meaning you must dig out the glue to unscrew. This will act as a tamper-proof indicator, so it will not be easy to hide the fact from DJI that you unscrewed it.