Some partial, and simple, deductions based on logic and no proof whatsoever:
1. Nitty would not have made the Black Ajah completely random, which would risk having all of one Ajah black.
2. Red and Green are by far the largest Ajah, and the odds of a black sister NOT hiding within them are very low.
3. Florida Man is Amyrlin Seat, and therefore guaranteed to be innocent. I am innocent, and therefore I believe one of John Wayne or Aizen is a black.
4. Blue and White would have one black sister from the two of them, not one each, since they're so small. Two chosen from gray, brown, and yellow, for a black group of 5.
1. Maerala Sedai, of the Red Ajah
2. Lord Genome Sedai, of the Red Ajah
3. Go D. Ussop Sedai, of the Red Ajah
4. Cypher Sedai, of the Red Ajah
5. Florida Man Sedai, of the Green Ajah
6. John Wayne Sedai, of the Green Ajah
7. Tiger Sedai, of the Green Ajah
8. Aizen Sedai, of the Green Ajah
9. Cooler Sedai, of the Gray Ajah
10. Dragon D. Xebec Sedai, of the Gray Ajah
11. Hero Sedai, of the Gray Ajah
12. Lord Melkor Sedai, of the Brown Ajah
13. Sigismund Sedai, of the Brown Ajah
14. Natalija Sedai, of the Brown Ajah
15. RemChu Sedai, of the Yellow Ajah
16. Ishmael Sedai, of the Yellow Ajah
17. Melodie Sedai, of the Yellow Ajah
18. Juan Sedai, of the Blue Ajah
19. Kvothe Kingkiller Sedai, of the Blue Ajah
20. WolfPrinceKiba Sedai, of the White Ajah
21. Nessos Sedai, of the White Ajah