title: Three-colour (simplex) Color Map in Matplotlib
body: <p>For a standard matplotlib color-map, the color-map function maps a number from a 1D simplex (from the range $[0, 1]$) to a particular color in such a way that the interpolation between the extreme values is smooth and interpretable. I have been looking for a way to represent three-class categorical distribution over a 2D space with a color map, essentially mapping each point on a triangular simplex (e.g. [0.3, 0.4, 0.2]) to a particular color, such that the colors smoothly interpolate between the extreme values at [0, 0, 1.], [0, 1., 0] and [1., 0, 0].</p>
  
  <p>Hence, I was firstly wondering: is there any general methodology for how to create visually interpretable and readable three-way color-maps like these? Secondly, are there any tools in Python or matplotlib available for generating such color maps?</p>