Millie should mate with Denver
Explanation:
Denver would be a mix between BB' and BB'. When crossed, you'll get BB (brown), BB' (light brown), BB' (light brown), and B'B' (white).
Charley would be a mix between B'B' and BB'. when crossed, you should get BB' (light brown), BB' (light brown), B'B' (white), and B'B' (white).
