Birth Control Switch

i was on the Depo birth control and I haven’t been getting my period since I was 16. but I switched to the birth control pill this Monday. The first 3 weeks the pills are yellow and the 4th week pills are brown. Does that mean I could possibly be getting my period back during my 4th week of being on the birth control pill or does the Depo birth control shot have to wear out of my system. I would assume that the pill will change my body and make my period start pretty soon. I don’t know , what do yall think?