I had a lot of trouble matching backgrounds of frames, widgets etc.. to the background of my website. I could only find matching colours after hours of trying... Until I found this free tool: Colorpic.
It is a simple and free Windows program that lets you zoom into any area on your screen - including into your browser window. With a magnifying glass, you go over an area, and it tells you the hex value of the colour on that spot of your screen.
Matching colours became a breeze for me.
More Blogging "Tips and Tricks", you find here.