Aaaaaargh,
OK, red boards = newer version in color. We got sick of the green ones, and they're actually easier to read and just plain cool.
differences on the board that coincide with the color change ?
Yes, some resistor and transistor changes in the input stages. Amp is more open and immediate.
However, these are not day and night changes. Does it make sense to switch to the new boards ? depends, would be $ 200. plus in exchange and up to everybody as to whether it's worth it. personally, I'd keep the old board, put in another $ 100. and go with the Extreme upgrade.
Late,
klaus