Values are more important than colors in painting. Values create depth and are absolutely critical.
Color is important too but a painting can be of any color scheme. I use the color wheel from time to time to improve my work. For example red and green go together.
Never leave a hard edge on anything you draw or paint. The subject must emerge into view and not look as though it were pasted to the canvas. I used to leave hard edges on some of my work and I blame the problem on my drafting background where hard edges are necessary.
Lay the paint on with quick strokes. Don't mess around with it. The more you play around the more trouble you get into.
