John and his wife needed their house painted. John wanted to hired Tom to paint the house. Tom estimated it would take 40 hours of labor at $50 per hour and 20 gallons of premium paint at $20 per gallon. John agreed to pay the labor charge but decided he would buy his own paint. John and Tom entered into a valid written contract for the painting of the house: 1 coat, 1 color, in 1 week, for $2000, John would supply all of the paint. John brought cheap paint. Tom immediately realized that the cheap paint was not covering as well as the premium paint and that 20 gallons would not be enough. Tom advised John that he would need more paint after the first day on the job.
On the second day, John's wife Marge decided that she wanted the 8 doors to the house painted a different color. Tom told her it would take an extra 2 hours and an extra gallon of paint. Marge agreed verbally. At the end of the fourth day (32 hours), Tom ran out of paint. The house was painted on only three sides. Tom had painted the eight doors in the color requested by Marge.

John refused to buy more paint. Tom did not have paint on the fifth day, so he packed up his equipment and sent John a bill for 42 hours of labor and one gallon of paint.

John believes Tom wasted the paint so that he would not have enough to finish the house. John hates the color Marge chose for the doors and says that was not part of the contract.

John refused to pay the bill.

What causes of action, if any, does Tom have? Can he collect for painting the doors? What defenses does John have?