I thought Walter would have chimed in by now......
Your on the money with the ID. "Y" Yamaha "2" 250 "88" 1988....If I remember correctly.
The other code is manufacture date. Possibly 5/10/1987.
As for colour, I have seen them in both colours for that time, so it was possibly a customer preference at time of purchase, although I never had enough money to buy a pair new in 88/89 so I couldn't confirm that