Here in Taiwan we use the same as they do in Bueno Aires...
Begginers - White
5th. Kyu - Yellow
4th. Kyu - Orange
3rd. Kyu - Green
2th. Kyu - Blue
1st. Kyu - Brown
Hakamas are only worn by Shodans and higher ranked students.
Also we don't touch the Bokken until Shodan either, and the Jo until Sandan. the ROC Aikikai organzation it seems to be very politcal (as they all are), and the training format by rank has become some what different from what is found else where.