Disaster! You've blended one color too far into the other. Everything is ruined! No, not really, what you need to do if this happens is to pick up a little fresh paint in the color that's at risk of being lost. (In this instance the yellow.) Then work back into the blended area from the outside (the area where the color is unblended).
Tip: Pick up less fresh color than you think you'll need. Usually it doesn't take much to restore the balance, and it's easy to pick up a bit more if you need it.
Whatever you do, don't despair. You can always do it again and again. And with a little practice, you'll get beautifully blended colors.
