Question about birth certificate

I am wondering how one knows the birth certificate#/file# of their birth certificate. I can't find them anywhere on mine (made in 1962, in CO). There is a # handwritten on the same line as the mother's mailing address. This is, of course, not the first birth certificate, but the one done aftr the adoption. Also, are all adoption birth certificates in CO black? Mom said that all of us that were adopted have black ones, and the birth children have white ones. Wondered if there was any significance to that. (They adopted 4 children, then had 3 of 'their own', though you couldn't tell by the way they treated us which was which. That's the way I believe an adoption should be. All my life, people have been amazed to find out ANY of us were adopted!!!) Margie