To lighten colors in watercolor, we add water. The transparency makes the color lighter. Oils and acrylics use white paint. So, then when do we use white paint? Often it’s to add a reflection after the object has been painted – an apple, a car, white caps on water. It can also be used to create some colors you might not have in your paint box. A pink for example. Cerulean blue can be made by mixing phtalo blue, cad yellow, and white. An opaque lime green. It has to be used sparingly or often turns colors mucky and streaky.