I find it easier to talk to new people in college rather than anywhere else. Now, of course college makes that process easier for me, but my confidence has been increasing ever since I started my college career, so it’s been getting better for me. Although, while I thought about this, I then realized that I had a question:
Is meeting new people easier in college rather than before we start our first year or after we graduate?
Meeting new people in college feels easier because you have something in common, a shared experience that makes a simple ice breaker. If you live on campus, it is especially easy to have the repeat contacts that form friendships and companion groups. If you maintain that feeling of confidence and willingness to meet people, it doesn’t matter when or where. Shucks, I was meeting people in the returns area at Ikea last weekend. 
There is no best time for meeting new people. Wanting to be around others is a human instinct. I have been able to meet new people my whole life.
Meeting people after college may not be ideal for someone who been struggling socially. You be working with people who have their families to take care of. Friends become a little less reliable because these friends have to deal with their own adult lives. Even though you are an adult and you are in college, most college students aren’t working full time, married, have kids, and etc. College is that transition from childhood to adulthood. During this transition, you will experience many changes. It is better to meet people during this transition than later in life unless you have good reasons.
I think all during HS many of us have been with the same people since Kindergarten. You are sort of put in a “role” (Jock, Nerd, etc) and it is hard to get out of it. ALso HS have more defined “cultures” on what is acceptable to wear, to do, etc.
College is like a reset. Almost Nobody has friends from before and it is a time to change your “role” and be who you want to be.