Connect the remaining wire to the in screw. Then the black or darkest terminal is connected to a black wire that feeds to the light fixture to get connected on the hot contact on the fixture while the white.

3 Way Switch Wiring Diagram Variation 3 Electrical Online
4 way switch wired wrong. Follow these steps to find which 3 or 4 way switch is bad. I put the old 4 way switch back and the light worked fine. Leave the light on. Connect the other pair of wires which lead to the second 3 way switch to the other pair of screws. From the first 3 way switch through a 3 wire cable the two travelers from the first switch are connected to the travelers on the second switch through the black and the red wires. Leave the light on.
As you will see most 4 way switch wiring is placed between the wiring of two 3 way switches therefore a 4way switch is installed with two 3way. Power enters the first light fixture box instead of the first 3 way switch box. If it does it is a good switch. If more than three switches are needed simply place more 4 way switches between the three way switches. A 4 way switch will only be connected to traveler wires never to a hot source or load wire and never to a neutral wire. I bought another 4 way switch cooper wired it exactly as the old 4 way and had the same problems.
If it does it is a good switch. Use a circuit tester to find the bad wire. This wiring configuration is no longer allowed as of the 2011 nec if a neutral wire is not present in the switch boxes. Now when wiring the traveler wires between switches make certain that when connecting to the 4 wayswitch that the 2 wires coming from the previous switch connect to a matching pair of screws on the 4 way switch and the other matching pair of screws on the4 way switch connect to the 2 wires leading to the next switch otherwise the switch circuit will not operate properly. Order is not important. Red wires on top and white on the bottom.
Alternate 4 way switch wiring is fairly complex. In the first 3 way switch box connect the pair of wires leading to the 4 way box to the out pair of screws on the switch. 4 way switch wiring 4 way switches provide switching from three or more locations. Also confirm that each pair of travelers on a 4 way are only connected to one switch per pair. Toggle the next switch to see if it turns the light on and off. Repeat for the other 3 way switch box.
If i turn the light off with the 4 way switch and attempt to turn it on with any of the other 3 way switches the light will not work. Toggle the first switch to see if it turns the light on and off. Toggle each switch until the light come on. A 3 way switch and a 4 way switch can sometimes refuse to work.