I often see many site or web application with an interesting combination of colors. I am very curious and usually looks the html source and study it.
With
Pain.Net I did a print screen and take the color that I like.
When I discovered Colorzilla my way of working is changed. With this Mozilla Firefox Plugin you can get a color on a web page directly with your mouse pointer. There is a preview of the color under your cursor. When you choose the color to take, left click with the mouse and this is all. The hexadecimal value of the color is automatically copied in the clipboard.