Cool Ash is a great product to use on lightened colour effects and particularly balayage, because balayage (on natural darker bases) tends to have a rusty or raw edge if it is not toned regularly. Therefore, Cool Ash is particularly good for keeping balayage effects refined and neutral. These same principles apply for the use of the product with traditional highlights and Ombre. Just remember, if these lightened effects are pale blonde, the effects from Cool Ash will cause such lightened areas to have a high ash or metallic tone. This might be preferable for a lot of consumers today (particularly brunettes), but if you like a crisp light clear blonde, you should (instead) be using Colour Restore Iced Platinum.