This was a fun experiment made in blender 2.8 and rendered in eevee. The watercolor effect was made with emission shaders and a massive compositing node tree. I also have the original concept made in sketchbook and an actual watercolor painted by my wife.
It’s really impressive! Man, the only thing sad about this is that you made such an awesome work and the end result does seem like a water paint
Great work!
For any colored material I used an emission shader, just so that it was a flat color. For the black “ink” lines I just used a flat black defuse shader.