Thanks! I did use the Shape plugin. Agreed, that pentagons and hexagons could be hard to tell. For colorblindness, I did use a color-blind friendly color palette: (the Okabe-Ito palette: https://thenode.biologists.com/data-visualization-with-flying-colors/research/). However, I do agree that color alone is not good enough of as a sole indicator for gameplay purposes. What would be better is if each color had its own unique subtle texture like this (from Geri Coady's Color Accessibility Workflows).
You are correct that the puzzles have multiple solutions. I do think with more constraints, the solutions could be more unique.
And the constraint with numbers in it means that that shape can only have that many neighbors (so because the two green shapes have two neighbors each (when they require one), the solution is incorrect). There's definitely more visual feedback I could give to convey this mechanic.
Thanks for the detailed feedback!