"My stomach has been bothering me, Doctor," complained the patient.

"What have you been eating?" asked the doctor.

"That's easy. I only eat pool balls."

"Pool balls?!" said the astonished doctor. "Maybe that's the trouble.

What kind do you eat?"

"All kinds," replied the man, "Red ones for breakfast, yellow and orange ones for lunch, blue ones for afternoon snacks, and purple and black for dinner."

"I see the problem," said the doctor. "You haven't been getting any greens....!"