The wires in trailer connectors in trailers are color-coded according to generally aligned regulations in the industry for safety reasons. The electricity in the trailer powers all of its parts. Common configurations of trailer wiring are:

• 4-wire trailer wire color code
• 5-wire trailer wire color code
• 6-wire trailer wire color code
• 7-wire trailer wire color code

All trailer wires have the same core of 4 wires and additional wires depending on which additional capacities they have.

4 Wire Trailer Wiring Color Code

The 4-core connector in trailers is the simplest and the most common one in smaller trailers without extensive functions. Here is the breakdown of the color code:

• White: Ground (-)
• Brown: Tail/Running Lights/ Side Markers
• Yellow: Left Turn Signal and Brake Light
• Green: Right Turn Signal and Brake Light

Tail lights or running lights are used to make the trailer visible to other drivers in low-light conditions, and they are a vital component of all trailers on the market. 

Similarly, all trailers have left and right turn signals. When you activate the left turn signal on the towing vehicle, the left turn light on the trailer blinks. Similarly, when you press the brake pedal, the left and right brake lights illuminate to signal that the trailer is slowing down or stopping.

5 Wire Trailer Wiring Color Code

The 5-pin connector wire is used in trailers heavier than 3000 lbs. These trailers have breaks that ensure safe speed. Brakes are regulated by a blue wire. Here is the complete color code breakdown:

• White: Ground (-)
• Brown: Tail/Running Lights
• Yellow: Left Turn Signal and Brake Light
• Green: Right Turn Signal and Brake Light
• Blue: Brake Controller Output

6 Wire Trailer Plug Color Code

Trailers with a 6-way connector often include a power or auxiliary power wire supporting additional features beyond basic lighting and brake functions. The meaning behind the colors in this trailer is as follows:

• White: Ground (-)
• Brown: Tail/Running Lights
• Yellow: Left Turn Signal and Brake Light
• Green: Right Turn Signal and Brake Light
• Red: Brake Power (or Auxiliary Power)
• Blue: Electric Brakes

6-wire connectors are used in trailers where 5-wire functionality is insufficient, and 7-wire functionality is unnecessary. These include livestock trailers, large utility trailers, camping trailers, and horse trailers.

7 Trailer Wire Color Code

A 7-pin wire connector is used in the largest trailers, such as RVs. It has an additional purple wire for backup lights or additional auxiliary power.

• White: Ground (-)
• Brown: Tail/Running Lights
• Yellow: Left Turn Signal and Brake Light
• Green: Right Turn Signal and Brake Light
• Blue: Electric Brakes
• Red (or Black): Battery Power (or Auxiliary Power)
• Purple: Backup Lights or Additional Auxiliary Power

Where to Buy Trailer Wires?

NNC offers multi-conductor PVC insulation trailer cable  in popular sizes: 12 AWG, 14 AWG, and 16 AWG. 

• 12 AWG wires are for high-current applications like electric brake wiring or auxiliary power feeds. 
• 14 AWG wires can handle the current for running lights, turn signals, and brake lights on small to medium trailers.
• 16 AWG wires are used for low-current applications (think LED lighting).