why does he go through red or blue lines?

It depends on how the line is drawn.

If you pay attention, the red and blue lines are made of two lines, a black one, and a colored one.

The rider will only touch the line if he is hitting the black line first.

Examples.

___->______  !|   If the ! sign was the black side of the line, and the | was the colored side of the line, and the rider was coming in the way of the arrow, and over the ____, he would crash with the line, because he will hit the black side first
___->______  |!   In this case, it would touch the blue/red side first, and so it would go through it.

You can change the way your line is drawn by drawing it from left to right instead of right to left, or from bottom to top instead of otherwise, just experiment with it.
Pressing shift will also change the direction of the line, though I have not fully tested that yet (just learned it 10 minutes ago).

Just play with it

im makin this track its mostly scenery but when i tap zoom out it goes all the way out so i want 2 no the button that keeps u at the same distance from when ur drawing the track[so when im drawing i can press play and the distance will stay the same]