What are the differences between redshirting, grayshirting, blueshirting and greenshirting in college football?

There are a lot of 'shirts in college football. Here's what they mean.

What Does Redshirt Mean? And The Reasons Why Players Do It?

What are redshirts, grayshirts, blueshirts and greenshirts in college football? - Quora

What are the differences between redshirting, grayshirting, blueshirting and greenshirting in college football?

Recruiting's color wheel: Redshirt, greenshirt, grayshirt, blueshirt

What Does Redshirt Mean in Football? (Full Explanation)

College football's newest trend — the in-season redshirt-to-transfer: 'Why waste a year?' - The Athletic

a green shirt - OFF-67% > Shipping free

College football scholarships

What are redshirts, grayshirts, blueshirts and greenshirts in college football? - Quora