This is a neat, simple concept! The presentation is very clean, and it was fun figuring out tricks like syncing up lines into a mixer so that it can then output more than one colour along a single line.
Unfortunately just as I was getting into it a timer would expire and I'd be booted out. I'd really like a mode without time limits where you can craft clever logistical solutions, perhaps with constraints on the total line length, number of mixers etc. To me that would be the kind of challenge that would suit this kind of game.
I think if you were to develop this further then the controls could be made way more intuitive and simple: instead of having to select NODE or MIXER, just click and drag to create a line that follows the cursor's path, then automatically place a mixer if the line ends on an empty square. Also might be worth using some kind of pathfinding algorithm to make sure that generated floors are actually physically possible to solve, had a few no-win scenarios.