Some of you may be confusing "suntan tropical" with "tropical worsted" uniform parts.
Or not. Lots of things picked up "aggie" names, too.
The history of uniforms at A&M is one of trying to leverage frugality, all while trying to follow US military fashions. After 1918, there were large stockpiles of uniform parts, all made to 'emergency' wartime spec. Those uniform parts were available, cheap, in bulk quantity. So, it made sense to stock the Military Warehouse with them in quantity.
In those days, one of the B uniforms was in and OD or "Midnight" green. This was worn in a green over green configuration, and also a green over khaki "undress" B uniform. The A uniform was, in sumer, a khaki single-breasted jacket over khaki trousers. (If memory serves, a 'light colored' shirt with olive tie was under the jacket.) Winter A was green jacket over green trousers, with light shirt and either black or olive tie.
Wool was the fabric used for formal attire in those days, so the stocks available would be the same. Wool, though, does not warehouse well without extensive moth protection.
Some of these uniform configurations can be seen worn by cadets in We've Never Been Licked.
Roll the clock to 1946. Again, huge stockpiles of unused uniform parts are stored away, available in big bundles, pretty cheap. Come 1949, the newly-created USAF switches to a blue uniform, and disestablishing their "Army Greens." In a similar timeframe, the US Army brings in the Midnight Blue A uniform, the "mint" green B uniform, and kept the TW (tropical worsted) khaki uniform (which actually has a "dress jacket" for overseas wear).
So, the cadet uniform was easily, and economically, provided from stocks of existing uniform parts.
This rolls on pretty well, other than if they buy 6 crates of TW shirts only to find that those are a wool blend, rather than a cotton-rayon blend--oops.
Then, near 1980, the Army drops the TW uniform entire. Briefly, the parts are available in huge quantities. But, no factories are making any any more.
Which is also part of the "boot debacle"--very few places make a quality military boot. The ones that do, are chock full of orders. If you need to order two thousand pair in demographic-weighted size cohorts, and you need economy, that will get you prices from people with "military style" boots.