If it helps, the original color timing had skies that looked either white or green but NOT blue.
April '99, interview with the DP / directors: http://www.theasc.com/magazine/apr99/matrix/index.htm
Because the entire film was meticulously storyboarded in color, though, Pope did have an understanding of the visual style that the directors wanted to create. "Larry and Andy wanted The Matrix to have two distinct worlds," says the cinematographer. "There is the world in the 2197 future — in which we have the pods made by the computers — and then there's the present-day Matrix world, which was designed to be a slightly unappealing reality.
"The future world is cold, dark and riddled with lightning, so we left the lighting a bit bluer and made it dark as hell. Also, the future reality is very grimy because there's no reason to clean it — only the pods need to be sterile. Because humans haven't actually manufactured anything for a hundred years, anything that had been manufactured is now old and rusty.
"We didn't necessarily want the Matrix world to resemble our present world," adds Pope. "We didn't want any cheery blue skies. In Australia, the sky is a brilliant blue virtually all the time, but we wanted bald, white skies. All of our TransLight backings [for the stage work] were altered to have white skies, and on actual exterior shots in which we see a lot of sky, we digitally enhanced the skies to make them white. Additionally, since we wanted the Matrix reality to be unappealing, we asked ourselves, 'What is the most unappealing color?' I think we all agreed on green, so for those scenes, we sometimes used green filters, and I'd add a little bit of green in the color timing."