This is a very basic watercolor tutorial about 2 ways to use the wet on wet technique.
Here are two very easy ways to add some texture when painting plain illustrations.
The first one as shown in the red popsicle is to drop some clear water, over a semi-wet paint. The water makes the pigment move in different ways, creating a lighter texture on it.
The second one is to add another color over the wet painting. If the first color applied is really wet, it will blend almost totally with the second color.