Visible light- and dual-curing composite resin luting cements were cured under porcelain disks of different colors to examine the effect of porcelain color on surface hardness. Knoop microhardness measurements were made at exposure times of 48, 72, and 120 seconds. Higher levels of hardness were obtained with dual-cured resin. Visible light-cured resin irradiated through colored porcelain required more prolonged exposure times to reach a degree of hardness approaching that of dual-cure resin. From the standpoint of microhardness, dual-cured composite resin is preferred for luting porcelain restorations of ≥2 mm thickness.