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I would love to be able to use an AnimBrush (in the Alpha Stamp setting perhaps) with a Hue / Saturation / Value jitter, controllable by a stylus property. This would allow for cool pointilist techniques.

yes Djm that would be a nice addition to the custombrush options.
but you can get close to this already by creating a custombrush
that is an animation going from white to black over say 255 (or 500) frames.

just draw your desired brush shape in 50% grey
stretch layer out to 255 frames
apply 'color adjust' effect (first frame brightness +100% , last frame brightness -100%)
this gives you the white to black transition
select all frames (by double clicking under the layer)
apply the effect
now pick up custombrush

you can now connect the animation of this brush to random
make sure step is about 50%
now you have a brush that looks very pointilistic

the problem still is that you cannot control the amount of variation, it is always Random.

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just thought of a possible work around for more control on the color variation
(is this possible guys?)

can you make custombuttons that choose a B color with a certain relation the the current A color, so you can speed-up the process of selecting the color range?

for instance if you choose hundred 100% blue as your A color you can make a brush that would choose a 20% lighter B color and one that makes a 40 % lighter and one for a 60 % lighter B color
and likeways butons that in the same way gradually offset the Hue value for a B color to whatever the A color happens to be at that moment

I vote for a gradient selection (like in the airbrush tool) but with some connections (random power, etc ...).