How to do know if certain person is right for us by salatul ishtikharah?And how to do it?

Answer

Salaatul Istikhaarah is not a divine revelation and it is not 100 % categorical. It is just a means to get an idea about the direction one should undertake. Simply one has to do 2 rakaats and then make the masnoon dua.

Dreaming the colours like white or green are considered as positive and black or red are considered negative. But it is not necessary to dream it. However one may go ahead with his project according to one's inclination after having made Istikhaarah.