1986 SR500 came in red with Shimano 600 components, six speed cassette, rigida rims. By 1988, they were seven speeds or more. This guy is telling you a story on age, unless he has documentation to go with it (very doubtful since he doesn't even give you model number). SR500 was suntour components in 1985.
1986 SR1000 had all Dura-Ace, including brakes, six speed, GP4 tubular rims, not sure about colors.
Suggest you check the vintage cannondale website (
www.vintagecannondale.com). It is a pretty good place to start.
First clue that this is not a mid 90s bike is the six speeds. Thats 1980s technology.
Id'ing a bike without pictures and more info is a guess at best.
Funny that sellers always underestimate age..... Has happened to me a lot, in fact on a similar vintage Cannondale. I had to educate the seller, to help him get more realistic on value.