For changing college after 1st year of your B.sc, provided that you should not have any backlogs in the first year. The college in which you're intended to take admission should in principal agree to admit you.
If you change your college under the same university where you're studying currently, you only need migration certificate.
If you change your college which is under another university, then you have to first get No Objection Certificate (NOC) and migration certificate from the institute where you're studying currently.