I'll need to add more bullywugs than the adventure originally used sometimes, due to the nature of the 4e combat system, but again that doesn't really change much about color. I MIGHT increase the size of a room, depending on what it looks like, but often that isn't necessary. And then I use the color from the adventure - because that is what matters to me.
But what makes this particularly interesting, frankly, is what this says about 4E compared to previous editions of D&D.
Because I can (and have) taken modules from 0E thru 3E and run them in virtually every other edition of the game. From 0E thru 2E I can literally do it without conversion: The stat blocks in a D&D adventure can be used without alteration in 2E and vice versa. Because 3E cleaned up and inverted the math, it's easier to just grab the appropriate stat block from the MM and plug it in, but the principle remains consistent. And with only a handful of exceptions (primarily giants and dragons, which kept having their power levels diddled with), encounter balance and design was incredibly consistent from 1974 to 2008.
But then we get to 4E and, as you say, suddenly that goes out the window because the game is fundamentally different on a mechanical level.
And that's hardly the end of the universe: I've run Tomb of Horrors in FUDGE, converted Exalted adventures to D&D, and played a Dragonlance Chronicles campaign that had been converted to GURPS.
But it does speak to how profoundly different 4E is compared to previous editions of the game.