how to get an new color preset

Hi, I purchased this quite good and elegant template. I changed some css in one of the css assets files but when I changed the logo from the admin and saved all my changes were erased to the default css file. Would that be possible to dupplicate some asset in order to get my own css presets. I'm not a dev guy and try to find what file generate those CSS but did not find out. I know some changes can be made direct from the less files but what about background color for header and footer for instance... Anyway I want to be sure that my css presets won't be erased by myself ore anyone else who would save something by mistake from the admin side. Thank you very much. Jean-Daniel