https://en.m.wikipedia.org/wiki/Mercury_Colony_Park#Sixth_generation_(1979–1991) Are the year spans for these generations correct? The 5th and 6th seem particularly long I guess?
I think they're basically accurate, but I have a slight bone to pick about their 5th generation - '69 to '78. I think it should have been split into two - '69 - '72 and '73 -'78. I think there's enough difference in bodies at the '72 / '73 juncture to make them different generations. I'm not a Mercury body expert, though. With the 6th generation, '79 - '91, there was a pretty big mid-cycle styling refresh for '88, but it was still pretty much the same body.
I'm no expert either, and I must add that FoMoCo has been known to stretch a platform or two across multiple decades (think FOX platform 1979-1993 or F-series from 1980-1996) but I have to say, at least from appearances the 1969 Colony Park have some similarities, visually, but clearly aren't carbon copies of each other. They very well could have the same, although updated, platform though. 1969: 1978:
"Platform" and "generation" usually refers to the suspension and frame system that the car is built around the overall body shell. Sometimes it's more obvious of the changes than not (such as GM's '76->'77 big car shift) and other years it isn't at all: the '70->'71 GM big car shift was touted as a major upgrade yet some of the makes you'd be hard pressed to tell from outside. Ford's Panther body style was around for +30 years but the first generation was considered '79-'91 due to the similarities and engineering documentation, even if the parts for a '79 wouldn't interchange directly with a '91. GM's B-body platform from 1977-1991 is the same way, even though a 1977-1981 car shares virtually nothing with a 1982+ car.
Grizz basic exterior did not change from 1979 thru 1987, although 1979 you could get louvers behind the front wheels as an option, changed front end in 1988 thru 91. dash panel changed in 1990, went to "bar" type speedo vs. the box type. some of the "wood" door trim changed, not sure if it was a model year change or a GS to LS change. 1979 Colony Park without cornering lights 1988 Colony Park