def assign_colors():
remaining = [(x, y) for x in range(8) for y in range(4)]
while remaining:
first = random.choice(remaining)
remaining.remove(first)
second = random.choice(remaining)
remaining.remove(second)
c = random.choice(COLORS)
pixel_colors[index_of(first)] = c
pixel_colors[index_of(second)] = c