Make colors assigned to users deterministic

[tyilo]

Otherwise we can't have matching colors on the webpage.

This line needs to change:

game/src/app/services/users.service.ts

Line 41 in cfc8ea7

user.color = this.userColors.splice(Math.floor(Math.random() * this.userColors.length), 1)[0];

It should be based on the index of the player, so shuffling the positions of players, would also change the assigned colors.