It's up to you (it's your site), but I wouldn't advise it. It'll just bulk up your stylesheet.
Remember it's automated - it picks up elements without background colours, for example, when they don't need one.
"Line : 2 Level : 1 You have no color with your background-color : body"
This first one is because you have shorthand css. You used background: #colour, but it looked for background-color:#colour.
As I said: bollocks.
This is the important bit:
Congratulations!
This document validates as CSS!