The Sun has evolved over millions of years, like any star so yes, it would have been a different size and color a few billion years ago. This is a very cool animation that shows how stars are formed.
https://www.astro.ex.ac.u.../BB2005_RT05_264.mov In another few billion years, the Sun's size and color will change again as it becomes a red giant. Even though we're in a stable time in the Sun's lifetime, where the size and color aren't really changing, the Sun is constantly moving and evolving. Nothing is stationary, which is why its so interesting to study!