I saw a B&W picture taken in 1950 posted on Facebook the other day of five Aggie cadets. One was obviously a junior with master sergeant stripes and was wearing the standard pinks and greens. The other four were apparently freshmen or sophomores and were wearing trousers that appeared to match their blouses (uniform jackets). By the time I was a Fish (1961), the entire Corps wore pinks and greens. Does anybody know when lower classmen were allowed to wear pinks and greens?

My dad is class of 58 and he wore green jacket and green trousers during his fish year

Try this:
https://www.thebatt.com/news/the-abcs-of-cadet-uniforms/article_25ea502a-4004-11e9-acea-97a4837f37d7.html

the correct answer is the fall of 1958: