In the past, Shading was an on/off toggle. In the original particle brushes (Optipuss), the shaded helms of grass or twiggs of a bush would quickly turn black, as soon as they started growing downward... A bit too dark too quickly for some tastes.

We have replaced the checkbox for shading with a slider which controls the black as a multiplier to the particle's colors. Move it to the right, and it does the same as it did before, leaving the shaded particles black. Move it to left left end, and the original color remains unchanged (multiplied by white it remains its own color). 

Anything in-between will let you keep a certain amount of shading, the way you like it.

Below are a few new painted bushes with the new shading.

Note that some of these also use another type of shading: the self-shading from ambient occlusion. This adds even more depth to it. The following takes just a few brush strokes: