I seriously did not know how to do this until last year (after scrapbooking for 4 years). It has saved my life. It is a good way to stretch your stash of scrapbooking supplies and get papers/elements/alphas to be the exact color that you want. And it's super easy.
step 1:
Open up your paper/alpha/element that you want to recolor. Make sure that it is the only layer open. I'm using the blue gingham paper from my farm kit. [. . .]
step 2:
Use your the eyedropper tool to select the color you want. You can click on a color in a photo that will be on the page if you want it to match. The color you choose should be the foreground color (it will be automatically unless you do something weird between this step and the next one). I wanted a green gingham, but it wasn't included in the kit. So I picked green from another green paper included in the kit so it would fit the same color scheme.
step 3:
Open up your Hue/Saturation box (found in Elements by clicking on the half white/half black circle in the Layers palette or go to the Layers tab and click on New Adjustment Layer). Check the box that says "Colorize".
step 4:
Adjust the hue, saturation, and lightness sliders (they are in the same box as pictured above) until you get the look that you want. The hue will change the color (but you already picked your perfect color with the eyedropper tool), so I just play with the saturation (usually has to be increased) and the lightness sliders. Then click "OK".
step 5:
When you change the color, you create another layer called the Hue/Saturation layer. This will make it difficult when you move the paper to other pages, or copy and paste from the paper. To avoid problems with this, merge both layers together. Remember when you close the paper to save it as something different so you don't write over the original file!
*You can do the same thing with papers with many colors on them, but the finished look isn't always the best because you can only recolor things to one color.*
