what do the colors mean? (pwm)
 

we are trying to wire a banner light sensor and we have to use a digital input from a pwm cable.

Which color wire on the pwm is the digital input? white or red? (we know that black is ground)

Re: what do the colors mean? (pwm)
 

white is input, red is 5v and black is ground

Re: what do the colors mean? (pwm)
 

If you are using a Banner sensor, you have to connect the brown wire to +12 V (with a 20 A circuit breaker per FIRST rules), the black wire to the RC ground (or, preferably, to the Breaker Panel's ground) and the blue or white wire to a signal pin of one of the RC's digital in.
I can't remember which one, but one of the outputs (blue and white wires) is NO (normally open) and the other is NC (normally closed). It doesn't matter which one you pick, as long as you keep that in mind while programming the robot.
You won't be using the +5V available from the RC, so it is better to insulate the red wire from the PWM cable.

Re: what do the colors mean? (pwm)
 

Unless I'm mistaken, it is the black and white wires on the Banner sensor that are the signal outputs, not the blue and white. The brown would be +5, blue would be ground, and black or white would be your output. When using the black wire as your signal pin, your default value is normally open (0 when unblocked). If using the white wire as your signal, it is normally closed (1 when unblocked).

Hope this helps,