You can change the color of a photograph in several ways, notably with the hue/shift sliders, or the selective color sliders. If you want the whole photo to be in shades and tints of the same color, you first desaturate it (make it black and white, but keep the RGB mode--instead of turning it into a grayscale image), then fiddle with the hue/shift sliders. But that doesn't quite get it, as all your blacks shift color--if you want a really light color the blacks become really light too.
HowEVER, if you keep your color photograph and add an adjustment layer (the little half black, half white icon at the bottom of the layers palette) of "Solid Color", pick your color, then set that layer's blending mode to "Color" as well... ta dah!! Now you've got a tinted photo, versus a colorized black and white. The contrast values are still really sharp, *and* you've got color everywhere you want! KEWL!
Here are two screen shots:
Desaturated, then recolored (click the "colorize" box) with Image-->Adjust-->Hue/Saturation (click on image to see more fully):
And now with the Color adjustment layer set to color blending mode:
The difference is really noticeable in Allen's pants, for example. I remember being bummed last year when Stef talked about being able to do this easily in CS3--in CS2 there's no explicit option for this. So, yay!