According to this article, there are at least two modifications of the V1 receiver:
Element IDs 4506085, 4566756 and 6040157 are actually Dark Bluish Gray.
Click on a colored part below to see the Sets and MOCs that use part 58123a Electric Power Functions IR Receiver in that color. You can find an overview of all LEGO Colors here.
If a color is missing, it probably needs to be added to a Set Inventory.