We need to know your theme, and then what sidebar you’re actually on about. You may think theres only 1 or two, but according to css style sheets, and templates you can have as many as you want in as many different colours. Usually, when you go onto the style.CSS press ctrl and F and then type in; ‘sidebar’ It’ll come up highlighting the name sidebar, find the one with a background colour, copy and paste the colour to make sure you have it for if its not the one you wanted to change, and just go through them.
Hope this actually came to any help.
