# Returns a coloured square for a defined colour id
	#
	# Assume colours are:
	#
	# * Green -> 0
	# * White (replaced with light gray) -> 1
	# * Red -> 2
	# * Yellow -> 3
	# * Orange (replaced with purple) -> 4
	# * Blue -> 5
	#
	private fun rubix_colour: String do
		if self == 0 then return square.green
		if self == 1 then return square.light_gray
		if self == 2 then return square.red
		if self == 3 then return square.yellow
		if self == 4 then return square.purple
		if self == 5 then return square.blue
		abort
	end