Jason,
Its the angle of the target, not the vertical slope. Colbert (and others) prefer a green angling left in a right to left wind, right in a left to right wind, since the wind helps the ball pattern go naturally to the angle of the green and increases the chances of hitting the target over cutting the ball against the wind. Colbert also likes the slope of the green to go downhill with the wind (in a L to R wind, slope sideways downhill to the right) I do that mostly for visibility anyway. As he once told me, "There are smarter guys than me, but if my lie slopes right, the green angles right, the wind blows right, and the ball rolls out right, I think I'm going to hit a fade, partner!"
That said, Fuzzy Zoeller has always said he "rides the wind" on tee shots (i.e. draw on a right to left wind) and "cancels" the approach shots to hit them straight. And, some architects also favor having the downwind side of the green higher to help stop a shot coming in with the wind, the direct opposite of Colbert. So, its not a universal concept, but its pretty prevalent thinking among pros.
They also feel that approach shots into the wind greens can be shallow, because the wind adds spin, and downwind shots require deeper greens because the ball loses spin and rolls out further. Into the wind, its just a matter of adding enough club to get the green, but stopping it is no real problem. I actually do vary the back to front slope of my greens a bit depending on the wind, although I don't universally make the downwind greens steeper and the headwind greens flatter. I mix them up a bit so the player needs to know which greens help him a bit and which greens will roll out a bit more. And, there is a practical benefit in making the short iron greens flatter - it makes it harder to hit and hold, and the ball marks aren't as severe.
BTW, for those of you who think this is modern tour pro gobbly gook, Geo Thomas wrote similar things, advocating long greens downwind for the same reason, and suggesting that the tail wind also reduces side spin, making a long narrow green a perfect choice for those situations.
Like Plummer, and even before, Thomas had it going on! (and, his thoughts on forming greens to the inherent physics of the shot and wind is also one of the quotes that had me opining on the concepts of fairness in the Golden Age on another thread)