This is an interesting lesson in the way that warm and cool colors can affect one another.
In this first example (oil on canvas - 14"x11") I made the tee shirt pink, since that was the true color of the model's shirt. I asked her to keep her hat on as a nice change from hair. But no matter what I did, the skin colors seemed washed out. Too much pink.
Having nothing to lose, I decided to change the shirt to a cool color. I chose blue because there is some blue in the hat and because the background was already green. The only change I made in the face was to lighten some of the highlights. It is amazing to see the difference. Now, I may darken parts of the shirt to break up that large monotonous area of light blue.