The source site for this is: http://wellstyled.com
This is a great tool. I know I will use it next time I am developing a design for a new site. This tool allows you to select your main color and it will suggest and display a variety of color schemes that you can use. You will have a choice of pastel scheme version for your color, a dark pastel, contrast and a few more. This is definitely a tool that every web designer should have it his tool box.