Changing Colours

I’m going crazy trying to work out how to change the colours on the main content block in this theme. I think there’s a base colour and the other two colours are different saturations of that base colour. Am I right? I read something about LESS files which made my head explode but also implied this was the case. I love the layout of this site but want to be able to change the colours.
Any help gratefully received.
Thanks

Jude