I talked to Kim a while ago about it and that's what their doing so we're following. She said Eddie had OK'd it though it sounds like exact criteria in up to the individual instructor.
"Nice to meet you. I am always excited to exchange ideas on my kids programs

Eddie actually has talked to me about what the ranks are for kids and "signed off" on it (he might have forgot

so here is the deal:
white, yellow, orange, green, blue.(we use rank Ts) They must be 16 to earn a blue which is equivalent to an adult blue. So, you should be able to rank them all. I am sure you could add stripes or something to give extra incentives as some kids will get promoted and have to sit at a rank for years depending on when they start. I have a kid who is a green belt and 12yrs old so he has to wait like 4 years to get blue!
Hope that helps and let me know if you have any further questions.
Kim"
As far as adult ranks ya most of the browns can rank to blue but ask Eddie as I am only purple and we have a Scott who is a black belt and ranks all but black.