Changing highlight colors in an elegant theme

I'm looking to change an elegant theme. They're all great, but I want a different color other than blue, green, red, or yellow. I already altered the files in the images folder to what I want, but that only changes the color around the blogger avatar. I'm sure there are some of the css files that need to be changed, but I'm having trouble finding where.

Could you please let me know what files need to be modified and what lines/codes?

Thank you.