Showroom colors are what they're entered in at shows, registration colors are what they have on the pedigree.
They're often the same, unless some of the colors are grouped together for showing. For example, otters: at shows they're just entered as "otter" and all 4 otter colors compete together, but on the pedigree is specifies "black otter", or "blue otter", etc.
Registration variety is more specific so if you're looking to see if something is recognized, it's better to look at the list of registration varieties