This great tool from ColorSchemer.com is pretty good if you want to find out more about some specific colors on a website or any other place on your computer. Maybe you saw a pretty nice website with some nice colors you want to use too. Just start it up and when you see a color you want to know more about, just hover your mouse on the color and click any key on your keyboard to lock the color. Now you have the values for HEX, RGB, CMYK and HSB as seen in the photo.

Its also free and available for download here