I want to buy an additional upper for my older Colt HBAR Match Target AR15.  What I am looking for is a 16 inch barrel.  I don't need all the bells and whistles, no quad rails or the like.  
Should I stick with Colt, or would a Bushmaster, Rock River or some other brand work as well?

If the finish matching matters to you, then you had better stick with an older Colt upper---the older Colt grey is vastly different than the black anodizing on all new uppers, including Colts. If it doesn't matter to you, then anything goes.
Another consideration is if your lower is a large hole or standard. If you want to use a small hole upper on a large hole lower, then a conversion pin is necessary.

Thanks,
The finish is not important.  I just want an upper that I can put on if social conditions were to dictate its use for something other than paper punching.
Its a large pin lower.