In 13w36a and 13w36b mesa biomes contained hardened clay and 6 colors of stained clay (red, orange, yellow, brown, grey and white). In 13w37a generation changed for mesa biomes - now layers are wider. But brown and grey layers of stained clay are removed.
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I played a world with seed -263424026 at coords x=1377 and z=1455, there is a mesa biome really without brown and grey clay. I think layer color and level position are generated from seed. Anyway, example on your screenshot confirms that this issue is invalid.
Seems to me this problem returned 1.8.1. / 1.8.9, the Mesa Biomes that i've found don't have the brown and gray layers in them....
Unable to reproduce.