I used the same gray I used yesterday to experience this color more. After my post yesterday. I got a few comments and emails mentioning that ultramarine blue and burnt sienna to make a gray. I used to do this combination, but I have stopped using it. I feel it is too purple. If you add more blue, it will turn too blue very quickly. That is because those two colors are not complementary enough. The mixing of the two does not neutralize enough. I still use those two for warm darks, but use them much less to get gray now.