I just wrote a lot of feedback into a comment, but itch.io took the liberty of just ditching it upon submit telling me I had too many characters. :)
Short version: Awesome entry! Love the Prison Breka level, would like to see more with multiple cubes.
Amount of colors is a bit confusing, but necessary to ease the back and forth level. Hardest thing was to understand why I had a connection start and end color, but I think that could get some useful functionality once you start making more complicated puzzles. Wish it would remember last chosen color combo though, now I'm clicking same colors a lot!
Also delete/remove button (shortcut: X) should be a button in the UI as well.
After watching the short youtube video I understood the concept and was able to pick it up nicely. :)