A combination of colors created by the mixture of two primary colors. For example, let's say you need green and purple, but you don't have paint for those two colors. You then take blue and red to make purple and blue and yellow to make green.
The lyric "oh girl" is probably the most cliche line ever... unless you're Dave Matthews. Instead of "You know I'd never mean to hurt you" you could have simply stated "you know that I'd never hurt you."