It's all down to personal taste in the end, I think mk2's look most modern in a dark metallic colour and I obviously like oak green. I was also looking for a mk2 in bright blue metallic (can't remember the paintcode but I read somewhere that only 500 came into this country) but I came to the conclusion that there weren't any 16v's made in that colour (you see a few G60's in it) so I would say that colour is pretty rare.
Then you've got stuff like calypso green (or was it capri green) and a couple of other shades of metallic blue which I can't remember the name of. You see far less cars in these colours but then that's probably coz they just weren't popular colours so nobody ordered that paintcode.
The oak green thing is a bit wierd really as the most popular colour for the mk1 was lhasa green which was quite similar.