those old kodachromes were wonderfully vivid, my dad had a load of old stuff on trannie, they make great slide shows.
perhaps the 'browning' was due to poor processing. when i used to work in a lab years back my boss took his eye of the ball on the E6 and subsequently the fixer wasn't 'repped' properly - one client turned up months later with a load of transparencies with a horrid green colour cast.
Paul.