Colgate Optic White Overnight in DENTAL ADVISOR Laboratory testing showed significant whitening after only 3 uses, and continued to show an exceptional whitening effect over 7 days of use. The average shade change in whitening index ΔW* was -16.1, or from a starting shade of C4 (5M1) to C1 (2R1.5) after 7 uses as measured by a spectrophotometer.