Irradiation with a very high intensity laser pulse (355 nm) induces blue color in TiO2 powders and films. The blue color, which is assigned to the formation of Ti3+ in the particle, persists in air for several months. With an increase of the concentration of Ti3+ in a given particle, photocatalytic activity is decreased because of a decrease in the thickness of the space-charge layer as deep Ti3+ traps are populated.