"Crimson Seedless" grape (Vitis vinifera L.) is a popular late-season red table grape in the California Central Valley, but its poor color development due to the warmer night temperatures in this region adversely affects the quality of this table grape. In this research, we evaluated the effects of new plant growth regulator named OR-151 developed by ORO AGRI on color development of "Crimson Seedless" in comparison with the untreated control and two popular plant growth regulators: abscisic acid and ethephon. Thirteen treatments were applied to "Crimson Seedless" grapevines including the control, OR-151, abscisic acid, ethephon and their combinations with and without adjuvant WetcitRTM. The berries were analyzed for fruit physiology, juice composition, external color characteristics, and skin anthocyanin content at harvest time. These treatments did not affect berry physiology and berry juice composition including berry dimensions, berry firmness, total soluble solids content, titratable acidity, and pH. Berries treated with OR-151 produced slightly higher levels of peonidin-type anthocyanins, as well as slightly higher levels of anthocyanin coumarates compared to the control. However, high variability in anthocyanin measurements limited the ability of the data to support more detailed conclusions about anthocyanin content and color development.