are all the rules (PDF file -- slalom is on page 85).
None of the sticks are ignored, it's just that the fastest way usually takes you much closer to some than others. What's probably the thing that's most confusing (and least obvious in a slalom, as opposed to other events) is that the rules don't say 'go around the pole', they say 'go through the gate', and in slalom the course is so tight that the arrangement of poles is very confusing to look at.
Racers must go between the two poles that constitute a single gate. It's not real explicit in that PDF, but I'm fairly sure that there's no required direction. Obviously when a gate is set across the hill they want to go through it going down, but when gates are set vertically, they can go through in either direction. There's usually only one way that will be fast enough to win, though -- remember, the top 10 finishers can easily be within a half second, total.
The red and blue just alternate so everyone can more easily pick out the pair of poles that go together.
By the way, if anybody cares -- the blue lines on the courses are not official in any way at all; they're just so the racers can see the direction of the course. Flat light on a solid white ground makes depth perception very tough.
This post was edited on 2/25 at 6:03 pm