If you're doing work with a Benjamin Moore paint, you will not have that many options in Menlo Park and Palo Alto for places where you can buy it. Thankfully, the guys at Grays Paint (both on El Camino in Menlo or Woodside Road in Redwood City) are friendly, knowledgeable, and fairly priced. They will mix your color while you wait. If you don't know what color you want, they carry call the color wheels.
CONS: Closed most of the weekend!