Charming post and great pictures! I just finally realized you have numbered ties? Where did you get them? I've had to use method like: line one, black ties on left leg, line 2, black on right leg, repeat with blue or yellow. This doesn't give a chance for individual bird ID however I usually hatch multiples then cull at suitable ages.....
That boy's color is a very typical result of either solid black crossed with anything colored or black being present in a mixed color flock. If you like this color, breed him as it;s a dominant color to get more.
Same thing with rose comb- if you like it, breed him to spread it around.
Blue legs on the potential top roo is due to him lacking the sex linked dominant gene called Id- Inhibitor of Dermal pigment. Breeding him with yellow/white legged hens will give you sex linking- daughters with green or blue legs, and yellow/white legged sons.
Your birds are showing a temperament I prefer.... cockerels settling rank mostly by simple posturing.. maybe a 'I meant this' peck or two, nothing more...
Mystique is a great name, for her hairdo and her partridge barring could be her morphing scales...