Doritos increased the intensity of their flavors and promoted it as Nacho Cheesier and Cooler Ranch flavors in the mid 1990's. At some point, the flavor names changed back to Nacho Cheese and Cool Ranch. Wikipedia mentions the recipe change in 1994 but not the name change.

So I'd place that bag design at around 1995.

That's C-3PO on there, so it's probably 1997-1999 (Special Edition was 1997, Phantom Menace was 1999).