feat: node color customize

[HaveF]

Thanks for this repo. It's quite interesting ❤️

Is your feature request related to a problem? Please describe.
#8 rename node is an essential feature. Another feature related is node customize.

Describe the solution you'd like
Customize is a bit complex, but I believe node color customize is a great feature to have, user can categorize the nodes visually by their color.

[transmissions11]

hmmm currently color is a pretty important signaler of node type, esp now that we have renaming. i think we could maybe allow color coding at the workspace level (#18) but don't think i want to add at the node level just yet