I realize this has been overdone many many times, but for those who don't know...

When you want to have a multicolored sig (like an abstract), just goto that little half black, half white circle under your layer window, click on color balance, and just mess around with the midtones. Don't too much with the shadows and highlights or it won't look good. Make another color balance layer, and mess around til you get a color that would look good blending in with the last color balance layer. Don't put too much on this one either or itll be dominant over the last one. After your done with the 2nd color balance, while selected in your layers window, goto Filter > Render > Clouds. Keep repeating the Clouds filter (Ctrl + F) until you find a nice mix. This is just a little technique (which is very useful and well-known to most graphic designers) for people who wanna know how to make things look a little better.

* NOTE: You can also use brushes instead of/with the clouds filter on the color balance layer. Try ones with feather in the brush, and low opacity. *

The best way to figure out why not to do something is to do it yourself (strictly speaking in the boundaries of graphics design....don't overdose on pills or anything :P ). You can do whatever with the color balance layers 'til you find something you like.

Thanks. Probably the most vague tutorial here....