I just noticed that in Sculpt mode, when you click on the big brush button in the tool shelf to select the brush type, some of the brushes are shown with color and some without color:
First I thought I had messed up my sculpt settings and tried to adjust them so that all brush types are shown with color. But then I saw that the thumbnails look exactly the same in the documentation.
Could it be that there's some deeper reason for the different coloring? Or is this really just some random UI inconsistency?