[Idea]: Add option for colouring by player

[edwardchalstrey1]

Requested enahancement or feature

• Currently edges and nodes are black. It might look good to be able to colour by player as in the Gambit GUI
  • working on add-colors branch - see Update testing for pygambit integration #23
• Add 3 color options: "default", "gambit", "distinctipy"
  • Ensure gambit choice looks good for many players
• Add a legend whenever a color option other than default is used