Here's a fun tip for you! I recently came across a new blog called Art and Influence (Link over to the right.) It's a wonderful blog run by two oil painters who are sharing their wealth of knowledge to the world. Anyway, I came across this Pic they have of a palette they recommend using, one that's devoid of secondary and tertiary colors:
This got me thinking, since I'm not a traditional painter (or even a painter to begin with, Hah!) Could this be replicated in Photoshop to achieve the same effects? So, I booted CS3, and pulled up my winsor newton swatches, and matched the colors best I could. Here's the result:
As you can see, I think it might work pretty well. The background for the palette is a neutral gray, and the brush I used was a simple round, no shape dynamics, opacity set to pen pressure, and the spacing on it set to 1% (The trick is to get a smooth even brush where you see no stamping. Anywhere between 1-10% will show this pretty well, just make sure you computer can handle it.) For the curious, here are the colors, and their respective color slider combos, in CMYK and RGB.
Titanium White: C: 0 M: 0 Y: 0 K: 0/ R:255 G:255 B:255
Cadmium Yellow (Pale or Lemon): C: 4 M: 0 Y: 89 K: 0/ R: 255 G: 243 B: 40
Cadmium Yellow (Medium): C: 0 M:31 Y: 88 K: 0/R: 253 G: 183 B: 57
Cadmium Red: C: 0 M: 94 Y: 98 K: 0/ R: 238 G: 49 B:36
Alzarin Crimson: C: 26 M: 97 Y: 91 K: 23 /R: 153 G: 35 B: 38
Winsor Blue: C: 100 M: 99 Y: 31 K: 21/ R: 41 G: 39 B: 98
Cobalt Blue: C: 95 M: 69 Y: 1 K:0 / R: 0 G: 91 B: 170
To actually mix these colors, you lay out one of the two colors you want, then start to lightly lay down the next color ontop of the previous one in the middle of the palette. When you start to see the color you're after, eyedrop it and cover that little mix you made with it, then take another primary color and work it some more, and so on and so forth. The trick is you mix the colors only with the colors you start with, not with any in the mix palette (though like with any rule, it's meant to be broken.) The reasoning is because you want to limit your choices to your starting colors, which should help unify your colors. For all the people that feel overwhelmed by photoshop's insanity of color, this should be a boon to have only 7 colors to work from.