The easiest way to color a black and white sig is by using color balance layers. On the layer palette, there is a series of buttons across the bottom, one of which is a circle that is half white, half black. If you click on that button, that brings up a list of adjustment layers that you can create. Choose "color balance", and play with the sliders you see there to color your sig. Check out www.good-tutorials.com, and search for tuts on coloring sigs to get additional hints.