Even though over 9000 people have already said this: I take a screenshot of the website, then select out a portion of the background and copy it. Then, I open up my new picture, paste in the small background color sample, use the thing that looks like a medicine dropper to get the color then fill in the background with it.

Also, do you really think someone who is too lazy to do the screenshot method is gonna take the time to use your method either?