NOTE: This has been merged into Matplotlib.
The colors begin with off-white, ranges through blue to off-black, then to red and back to off-white. Perceptual lightness contrast and color contrast are uniform over the whole value range. The colormap prints as perfect white-black-white, and works equally well with color blindness.
Note that the small ripple in the perceptual deltas are the result of only using "only" 35 color steps. If you need more color steps, they are defined in red.py and blue.py.
The colormap was designed using the viscm colormap design tool by creating a perceptually uniform colormap from off-black to off-white through red, and another colormap from the same off-black to the same off-white through blue. The files red.py and blue.py are still editable through viscm.