It won't reflect green after time of period,it depends upon how much feedbacks you have from DT level member and also DT depth level.
It will be green after 5 months, IMO. Initially, the trust score remains black only and later it turns into green. I don't know at what point at turns into green. For example, user shasan receives positive feedback from hiriousandco, a DT1 member. But still his feedback is black.
While user Darth0ne had received positive feedback from DT-2 member haploid23 which has already turned into green.
Oops,I thought the trust score will be based on the depth level of the members,so anyone knows how long time needed for a feedback to turns into green and what is the purpose of green into black after some time?