Names not Kevin but here are my thoughts...even if colors change (darker or lighter) usually the shape and size and basic coloration are the same, so if you are taking only offsets (or leave cuttings) then you probably won't significantly change what you have...however I think large scale growers take seed from their named varieties and call these seedlings the same cultivar - this is where there is a significant potential for change.
Or you could get a naturally occurring sport but again, it would look very different
