Well, I have been searching for a grey Colt four positon receiver extension for my early M4gery.  

I haven't been able to dig up anything that confirms that a Colt 4 positon receiver extension came in grey?  I understand that the XM4 "era" M4s were outfitted with 2 positon extensions, and there doesn't seem to be a solid consensus as to when the 4 positon extension showed up.  I plan of this rifle not only being nostalgic, but it will be a go-to KISS rifle, so I prefer the four position, especially when wearing a vest (comes with my profession).  I wish I had paid more attention to the few fixed handle M4s that were floating around when I first entered the Army.  The PLTS and PSG's had them, I recall the grey finish and funky lock rings (pre-castle nut).  I don't remember if they four or two positon extensions, but they were cool compared to our mixmaster M16A2's (or the sloppy beat the hell malfunction-o-matic M249 dropped into my cherry lap).  

IF it came in grey, was it anodized as such (like a two position), or was it grey coated over black anodized, like we find on '70s A1 extension?    

I'm half tempted to just have an extra position milled into a grey two position extension.  I understand that this practice was common back in the day... but if a four position grey extension didn't happen, I don't want to spend $$$ to devalue an expensive part.    

Any input is appreciated.  

I was told the XM4's had 4 position extensions. Part of the XM4 improvements.

IIRC it was Coldblue who stated that.

I also found some pix of XM4 rifles, which appear to depict a black receiver extension.  I'll run with it....

Thank you.  

I found and bought one off another reputable member who's a long-time Colt parts collector for my XM4 build.  Anodizing is a lot darker than the extensions from the 70's and late 60's.  Yes, I paid more than I should have.  But it could pass for new old-stock and came in opened, but original Colt marked baggie.  I'll get pics up when I have a chance.

They pop up on gunbroker, and the EE.

Be vigilant, and patient.