Coolant question

Just replaced my radiator on my 2001 tacoma prerunner with the 2.7 liter 4cylinder engine. I bought a gallon of the red antifreeze from the dealership, mixed it 50/50 with distilled water. I think I need to add a little more. Can I just add more distilled water, add the red/pink from an auto parts store, or do I need to go back to the dealer to buy another gallon of the red stuff?