The pill , help!

Hi ladies i recently decided to switch my bc to the pill the doctor didnt explain to good and the info packet doesnt help either. Cam someone help me out by telling me do i have to start on the day of my period or can i start anyday? Are the numbers amd days suppose to match up as todays date or does that not mean anything? Or are the numbers just for the number of the pill your own? And why are some blue and some green? I know i shouldve asked all this before i left but i didnt think it would be this confusing