In Photoshop (or any other program), is there a way to define a brush from an image and retain the colour of the image in the brush, without it being converted to grayscale (and then becoming monotone of the colour you select while painting)?
Alternatively, is there a way to change the hue of a grayscale image, e.g. make the darker tones more red, the middle tones more purple and the lightest tones more blue?
As far as I am aware, colored brushes are not possible in Photoshop.
As for your alternative question though, definitely! Just use gradient maps. For instance:
If you have a grayscale gradient like this:
And you apply the following gradient map to it (accessible from image/adjustments or as an adjustment layer):
You'll get the following new gradient:
Here's how a similar gradient map it would look with a normal grayscale image:
...a bit of a hideous example, but gradient maps are amazing and quite useful.
