graphicxtras.com > Photoshop brushes in different color modes/ image modes such as RGB LAB CYMK 32bit etc tutorial
You can use the Photoshop brushes in CMYK / LAB and other color modes / models as well as RGB
1) Image menu and mode followed by CMYK
2) Go to the brush tools in the toolbar
3) Apply stroke in CMYK color mode etc
To go back to RGB, just go back to the same image menu and select the RGB option
You can also apply the brush stroke to CMYK's color channels, select individual cyan, magenta channels via the channels panel. You can use the dabs in CMYK to create some truly extreme color effects, especially combined with the black channel.
Image menu and mode and LAB. Apply the strokes as you would in RGB. You can also apply the strokes in different colors to LAB channels L and AB channels. The generated dabs seem to be a lot more subtle in LAB mode, more diffuse.
The RGB option is available for 32 bits channel mode via the image mode menu. In 16 bits / channel RGB LAB CMYK are available for the strokes. Some of the filters are not available in the 32bits etc. In all the examples I have been using the default standard soft round. With 32bit and 16bit channel, you also have the added feature of the HDR toning when you convert back to RGB 8bit so the results can be displayed on web pages etc and the HDR toning has a large number of presets as well as settings to either create very close to the same result (visually) in 8bit and 32bits per channel but you can also use the settings to invert / grayscale / added saturation etc. The result can be very different from the actual generated brush strokes.