Using the Splatter brush
I lay in a background, mainly using the Modern texture, and then I blur that at around 75%. After that I go crazy with splattering different colors, stopping to blur every so often at around 30%. I keep doing it until the entire canvas is colored, and it is pleasing to my eye.
Just have fun with it, and see what crazy creations you can come up with.
Please let me know what you thought of this video tutorial. TIA.