blue tubing, buying coolant it way to expensive. I ran red coolant on one of my builds and the inside of all the blocks and tubes are now stained red, the res I had was a double 5.25 bay with a clear front. when the coolant lvl dropped it would leave a line so the top half inch of the res looked nasty.
Its easier to run distilled water with a kill coil with blue tubing. you will thank yourself in the long run.