Allow user to configure contract color

[SyedAhkam]

It would be nice to allow the user to set a color to a specific contract.

Could be asked while adding a contract or let them override the default later on.

This would make it easy to assign a color to them on the overview page.

[SyedAhkam]

@0x0elliot would need changes to the backend for this.

[SyedAhkam]

after this, I would expect /monitoring/overview-data to return a color for a contract appropriately.

[0x0elliot]

gotcha. getting to this.