I read a book at some point in school in which children travelled between worlds with colored rings, I don't know why, but I have always remembered this and am very curious as to the name of her book, can anyone help?
Sounds like Spaceling by Doris Pischeria to me. I remember reading this book many years ago.
The ability to see other-dimensional rings that float in Earth's atmosphere was a late mutation of a few space-age humans. Daryl was under the care of the institution for muters, and she had discovered that if you jumped through the right ring at the right time it would land you in another dimensional world and another shape.
The first thing that came to mind for me was The Seventh Tower Series, but I'm not sure it perfectly matches the description (as far as I can remember there were colored rings in the series, but I don't think they were particularly central to the plot).
I believe you are referring to the book "The Magician's Nephew" which is the first book in "The Chronicles of Narnia" series by C.S. Lewis. The children, Polly and Digory used yellow rings to get to different worlds and green rings to return to their own.
My reference for this information was just having read the book.