I've heard that they made some Sand colored frames for a distributor years ago, but I've never seen one of them, it's just a rumor as far as I know. Supposedly it was the same color as their Sand colored knives.
I heard another rumor that there were some prototype gray frames made for an LE contract.
Glock 27's have only even been offered in OD. OD can vary, some of them can be lighter, some much darker. Besides that, the appearance of the color in pictures can vary quite a bit due to the lighting. If it's not OD, it's an aftermarket coating.