Im thinking of buying an 90HAM with original case and OCA, however its one of these models where the color has turned from blue to green over time. Do you think that diminishes the value of the guitar at all? Is it due to poor care of the guitar? I still see plenty of 90HAMs online where the color is still blue, so not really sure why some have retained its color while others have not.

It's usually exposure to sunlight (UV rays) that causes finishes to change colour. Some look better for it, I think!

The 90 HAM seems to be the only PGM model where I've seen color changes over times guess the ones that are still blue have been mostly stored in cases the whole time.

Found one 90HAM around 8/10 condition, selling for 3600 USD with original case and OCA, its too overpriced but these guitars are to hard to come by that I'm thinking about it