These are a couple of trial in studying the form/content of the drawing.
Reference that can be applied in drawing canvas:
Text Character Paint (Text Rain by Camille Utterback & Romy Achituv )
Pattern (from Processing Example Sketch )
I have not being able to use pattern and drop paint for now.Considering the aspect of playable,they are interesting. Pollac paint is possible to build and can become an iteration. However, content of how they can be applied in art therapy is lacking crucial support now. It can be viewed also as a digital format of simple/simplistic app to draw this effect without mass preparation. How physical format is different than digital remain a issue standing there.
This is especially studying on applying color plate inside the app.
Simple Color testing
a progress sketch in applying simple color because the spectrum draw filed to be applied in tablet.