I could be wrong, or they may have changed, but last I recall I think that Colt was no longer refinishing aluminum. I would definitely contact Colt and ask, because the guns they were not doing were revolvers and that because of the risk of cracking the frame during barrel removal.
They may well do automatics.
If not, here's several top gun refinisher services who do top quality aluminum gun anodizing. Note that standard anodizing services are not licensed to do gunsmithing and it's a Federal crime to work on guns without a FFL license.