Was the Receiver anodizing on the XM16-E1, M16 A1, Colt 607 and Xm-177 E2 all the same general color. That being the blueish grey or did they differ and how. I’ve read here that Norrels Moly Resin Flat Grey is a good match but that their Grayish flat black is also, but I don’t know what would be good for what model. Thanks

Get the Gray/Black.  The item will come out looking overly gray but once you oil it it will be the correct color.  It is very forgiving and easy to clean up or touch up until you cure it in the oven.  The duration and temp has an impact on the overall color too.  It calls for 300 degrees for an hour.  If you aren't watching the temp and it gets hotter it will take on a more brownish color which is hard to duplicate.  Do the upper and lower together if at all possible if having them match in color is your goal.  I always cured them at 290-300 degrees for 1.5 hours.

Thanks for that. It that the grey/black or the grey/black colt. Also does that paint neet to be thined to paint?

It’s the Colt Grey/Black Flat.  It doesn’t need to be thinned

GRAYISH-BLACK COLT FLAT – Color is specifically mixed to be the best match for Colt XM-16, M16-A1, AR-15 SP1 rifles from the 1960s through mid-1980s. This is the color and product commonly being used by manufacturers, refinishers and individuals for early Colt M-16 and AR-15 retro project rifles.
https://www.norrells.com/moly-resin-application-instructions/

The upper is original Colt XM grey anodizing the lower is Norrells Colt Greyish Black Flat.