Your best bet is to go with an RRA or Stag, with Stag being the best value IMO, RRA's a bit more, but they have name recognition and that sells for them. In the end, to truly get a good color match, you really need to hand match the upper and lower yourself.
Are you near a dealer that sells lowers you could purchase from? The reason I ask is because it doesn't matter what brand you choose, color mismatches happen. I have 2 Colt LE6920's for instance - both bought as complete rifles. My first one did not match up exactly, and it is very noticeable outdoors in the light. My second one matches perfectly. I have seen this with BM, RRA, etc....alot of the big-name manufacturers. It is usually infrequent. Good luck with whatever you go with, but hand match them if finish match is important to you.