What do the colored lights by the doors of the trains mean?

Hey, this is my first post, but I was wondering if anyone knew what the colored lights by the outside doors to the trains ment. I believe there's a red, yellow, green and blue? Thanks!

As with most commuter rails and sytems, the lights outside the door, basically tells the conductors and engineer a visual status of the doors, red means the dors are open, green that they are closed, yellow and blue I have not seen yet.

One of One-Sixty wrote:As with most commuter rails and sytems, the lights outside the door, basically tells the conductors and engineer a visual status of the doors, red means the dors are open, green that they are closed, yellow and blue I have not seen yet.

Not necessarily....on LIRR M7's, here's what they mean:

Green = air brakes released in that car
Yellow = air brakes applied in that car
White = trainman controlling doors from that door panel
Red (blinking) = parking brake applied in that car
Blue = Automatic Speed Control active (Controlling car)

M1/M3's are similar as are C3's.