Once you have the GFCI wired up, you can double-check that you have the wires on the correct terminals by using the test button and seeing if the GFCI receptacle is still active. If you have the line and load switched, the GFCI will turn off all the downstream outlets, but not its own (which is unprotected)--at least that is the way the vast majority of GFCI receptacles work.
The color of the plastic for the receptacle is completely immaterial from the point of view of function. It may or may not be immaterial to the interior decorator of record for the RV.