People often ask if I find colouring-in mindful. I would say yes, but I colour-in in a different way. I don't really colour-in colouring books; but my own illustration work. Here is an example of the type of mindful colouring-in that I enjoy doing.
Before working on the line drawn designs in my colouring books, I tend to start my initial sketches using paint and pencils. Observational drawing and painting is my form of art mindfulness.