The one on the left is Sennelier Acrylique Warm Grey, and the one on the right is Old Holland Warm Grey Light oil paint. They're both pretty similar which is good for matching acrylic colors to oils if I need to do that. They are so warm that they're almost brown in color (in fact, both these colors are a mix of browns with white). I've added titanium white as a tint and mars black as a shade on both of these for comparison.
The tints are really nice, great for highlighting, light dapples or to incorporate into the base color for white markings or a grey horse. The darker shades are great for greys again, muzzles, and also for some grullo colors. Out of the tube, these greys would make a great base color for a classic champagne (haven't tried that yet but it looks like it would work), or a dun or brownish grullo color. They're also a good base color for chestnuts, can be mixed with a darker brown, black, etc. for a variety of grayish-brown colors. Very versatile!
The Sennelier acrylic is pretty thick so will need to be watered down before use, and the Old Holland oil is thick also, so you might want to try a medium or thinner to help smooth brushstrokes. I used to hate how thick and hard Old Holland colors were, but I really like this color so I've gotten used to it.
