To add some completeness to this thread, stereo_gui can now colorize images and show a colorbar (
https://stereopipeline.readthedocs.io/en/latest/tools/stereo_gui.html#displaying-colorized-images-with-a-colorbar-and-axes). (Also can do color scatterplots.)
This feature uses a different paining approach, based on Qwt, and is not yet integrated with other stereo_gui features (such as overlaying of images, zooming all images to same region, hillshade, overlay of scattered points), that will come later. For now this is in the dev build (accessible from the GitHub release page, and as usual, installable without admin rights).,