OK Here's a little shader setup I use a lot. I don't have a name for it, but I use it to manipulate textures to be the color I want.

We start on the right with some color map - whatever original texture.

The middle Color_Math:Subtract is finding out how the texture map differs from some reference color. Here I actually sampled a color from the texture itself.

So the subtract is producing positive and negative delta colors (colors that represent the difference between two colors). The more the texture is different from the reference color, the more positive or negative the delta color will be. We cannot "see" the negative delta colors, but they are there, for sure.

The next step, on the lower left, is where I multiply the delta with a factor. If I use a factor less than 1, I decrease the delta color intensity. If I use a factor greater than 1, I increase the delta color intensity.

Finally, in the upper left Color_Math:Add node, I add back the reference color.

When the same color is used in both the subtract and the add, this serves to simply control the intensity of color variation, around that reference color.

However, when I add in a color that is different from the subtracted color, then I can actually shift what color this produces in the final output.

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