PURPOSE: To prevent rupture of a paint feed pipe communicating with a paint valve for spray cutting and damage of color change valve assemblies by permitting immediate on and off paint when the above-mentioned paint valve is changed so that the paint can be circulated at all times in the feed pipe.

CONSTITUTION: A solvent in a solvent tank 26 is first fed to clean the pipeline from the 1st color change valve assembly 21 to the 2nd color change valve assembly 51 and the expulsion of the paint and drying are executed by the flashing air from an air valve 30 at the time of a color change. The paint of the color after the color change is then delivered from the assembly 21 through the assembly 51 to a paint tank 22 of said color without mixing the same; thereafter, the paint valve 41 for spray cutting is changed over to deliver the paint toward a painting gun 43. As a result, the rupture of the feed pipe communicating with the paint vale 41 from the assembly 21, the damage of the color change valve assemblies and the exertion of undue stress to pumps are obviated and the on-off response delay at the time of changing over the paint valve 41 is eliminated.