Where did we see LaForge and Riker were in the same graduating class?
It's on Memory Alpha, and I can only imagine that the dates were taken from a screencap of personnel service records shown briefly in "Conundrum".
I was under the impression that they were around the Academy at the same time with Riker having had just gotten out and was committed to an assignment still around Earth (such as the Shuttle Run described in Chain of Command) while LaForge was in his first or second year.
No, according to MA, they were in the Academy together from 2353 to 2357, after which Ensign Riker when to the Pegasus
and Ensign LaForge went to the Victory
. They eventually ended up on the Hood
together, but by then Riker was XO (supposedly) and LaForge...wasn't. I don't know what he did wearing red. General junior officer stuff?
I like backstories in characters, and sometimes the writers develop one for their own use, and sometimes characters just collect random factoids which become a backstory. That's how most of Kirk's backstory came together. Sisko's apparently came together in much the same way.