Commodore went from red to green power led's in their A2000 when the Rev 6 A2000 was introduced. Same happened with the A500. Red power led usually means you have a rare rev 3 (the one with the C= left key instead om Amiga key) or a rev 5. Rev 6a machines usually have a green power led. All (original) rev 8A (500's and 500+'s) all have a green power led.
Thanks for the detail. Both the A2000 Rev 6 and A500 Rev 6a appear to have been made after WB 2.0 was released, so that means they're both made after (or in) 1990. That makes it easy - if you've got a green power LED, you've got a 90's Amiga.
I think it also has to do with cost. Green LEDs didn't really get made in volume until the mid-80's and they were probably more expensive. By around 1988/89 they probably came down in price and that's when manufacturers started switching.
Of the 25 80's/early 90's computers I own, only the Apple IIc doesn't follow the pattern. It and its matching monitor have green power LEDs and they were made 84/85.
