Above is a hip bone, called the "innominate bone by some anatomists. Innominate means "without a name". So it is the bone that has no name.
There are colors that have no names. An innominate color is a color that isn't identifiable as red or yellow or blue, you wouldn't call it green or purple, it is a gray but it does have some color to it. Who knows what to call it?
Nature outdoors is full of innominate colors. They make your other clearer colors sing. Without them your picture has no color variety. Just as you need darks to make your lights seem bright, you need innominate colors to make your purer colors sing.
ALL COLOR IS NO COLOR!
Below is a Monet of Venice. I have drawn some crude arrows on the painting pointing out some innominate colors. I don't believe Monet made those notes using black or earth colors, they are a mixture formed from all three of his primaries.
image from artrenewal.org
When I am painting outdoors I often mix my innominate colors this way. I put a spot of my red, a spot of cadmium yellow and a spot of blue next to one another on my palette. Then I pull the middle of them together with my brush, giving me an innominate color. I can then make redder, yellower or bluer inominate colors from my pile. You could say it was a mud color, and I suppose it is, but I can hit a lot of the colors I see before me in nature out of variations pulled from this pile.