'Trimester' reminds me of what a pregnant woman goes thru...

Anyway to clarify, a cadet earns his white bars as he progresses
thru the course, starting with 1 white bar (and a white lanyard)
the first day he steps into OCS...
1 white bar = Tri-service term
2 white bars = Service terms 1 and 2
3 white bars = Professional term
... till he receives his black bar at his commissioning (actually
before, haha).
As for white colour singapura, its for all OCTs, not just for navy
midshipmen.