I think around 88-89 or so. Maybe even 87, because I´ve seen some blue stripes with serial# not much higher than mine.
My red stripe was made in march 87 and the serial is around 19200.
And I think then green stripe came out in late 89 or early 90.
But there seems to have been some overlapping between the various stripes, so it´s hard to say for sure.