Cassidy Williams recently published an open source calendar that might scratch that itch: https://pocketcal.com

Source at https://github.com/cassidoo/pocketcal

No drag ability but you can put different color data into a data JSON file that gets used when rendering for Neatocal [0] (fork/extension of Neatnik's calendar).

Example: https://abetusk.github.io/neatocal/?data=example/sched.json

[0] https://github.com/abetusk/neatocal