I love color. All colors. Which made it very difficult to narrow down the color choices for my wedding. Unless you have something specific in mind from the beginning of your wedding planning, it can be very hard to make a color decision. Even with 4+ years of art school, I always use design tools to help visualize my colors.
Adobe makes my favorite color theme generator, Kuler. Their free tool is not only extremely helpful, but really fun to use as well. You can explore all of the user generated themes or experiment with your own color variations. If you have one color in mind (mine was turquoise), you can use that as your base and experiment with all sorts of color combinations, like complimentary, contrasting, monochromatic, etc.
You can even upload an inspirational photo and Kuler will generate a color scheme for you. In the example below, I uploaded an image of our ceremony site and a lovely beach inspired scheme was created for me.
If you register for an account first, you will be able to save all of the schemes you come up with. Once you decide on your perfect colors, you can use the provided RGB, CMYK, and Hexadecimal codes for all of your printed material, on your wedding website, and to help choose dress colors, flowers, linens, etc.