An investment of a little time gaining a basic understanding of colour theory will repay itself a thousand times over. It's worth buying (or downloading) a colour wheel as a handy reference when you're learning and don't forget it has 2 sides, one side will help you with the practical aspect of mixing colours where the other side will help with the more abstract area of colour relationships, in other words - what colours work well together (women know this naturally, it's in their dna or something, but this is the area where blokes need a little bit of help).
Trust me, you will never regret spending a little bit of time on this. Before I started looking into it, for example, I would never think of shading yellow using purple or shading red using green but it works...no really.