Tests: check color classmethods on instances

[AntonisDevStuff]

See: #3456 (review)

As suggested, tests for all the from_* class methods of Color can be added to check their use to an instance.

for example:

pygame.Color(0,0,0).from_normalized(1,1,1) == pygame.Color(255,255,255,255)
pygame.Color(1,1,1).from_cmy(1,1,1) == pygame.Color(0,0,0,255)
pygame.Color(255, 0, 0, 255).from_hex("#00FF00") == pygame.Color(0,255,0,255)
...

Note: the value of the instance doesn't affect the result.