I agree with the let it be crowd. I have one that started out like yours, small and translucent. Today it is a lot bigger (~12") and only slightly less translucent, despite spending the last 2 to 3 years under about 300 par lighting at it's current chosen residence. It did develop a very nice pink shade to the outer ends of the tentacles with a more blueish tint towards the base. The oral disk is still very translucent. Same white speckles remained. It did lose it's bubbles though (high flow area).
(My pics don't do it justice)
So as the others are saying, just keep your water good, let it crawl until it has found it's happy spot (and it may change it's mind a few times) and you will most likely end up with a beautiful happy nem! Enjoy.