How can I create a map with cell values being mapped to a ternary color space?

[poster]

My idea is like this: assume I have built a geographically weighted regression model, i.e.for each cell, y ~ β0 + β1*x1 + β2*x2 + β3*x3, I want to create a single map showing the relative importance of the three variables on the response variable y.

I want to do this like this: (1) I normalize the three coefficients for each cell into unit 1 by dividing each coefficient by their sum; (2) I utilize a ternary color space to map the three adjusted coefficients to a color code; (3) I get the color code and fill it into the corresponding cell.

But I don't know how to implement this in practice, like R, Python or Matlab? Attached is the ternary color space.

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