No, this painting is not a watercolour painting. It has been painted with acrylic inks (a medium which is used by airbrush people, but you can apply the paint also with a brush). You can apply the ink in a wet-in-wet technique: wet the paper with one brush and then apply the colour with the other, and water it down with the first brush. You have to be quick because this medium dries quicker than you think it does. The less water you use the more opaque the paint is, and the more water you add the more translucent it gets. Because of the high pigmentation the colour is still very vivid and strong.