I need to switch out a 3 way dimmer switch and have never done it before. I watched some youtube videos but wanted to check and make sure i do it right.
When I pull my switch out I have a green,red,red,black wires coming from the switch and I have a copper,black,red,black wires coming from the wall. I see that the green connect to the copper, one red connects to the red, one black connects to the black, and one red connects to the black from the wall. My question is how do I know which red goes to the red and which red goes to the black from the wall? Or does it not make a difference. I hope this made sense.

 

It makes a great deal of difference. What are the installation instructions for the new switch? Does it have the same set of wires as the existing switch?

Every 3-way switch connects to two traveler wires and one power wire, either line or load. It sounds like your old switch may be designed so that the two red wires are the traveler connections and the black wire is the power connection. If so, you need to identify which wires in the box are the travelers and which wire is the power wire.

Typically, the travelers are a red wire and a black wire that are in the same 3-conductor cable (black, red and white) and the power wire is a black wire that is in a 2-conductor cable (black and white). What cables do you have coming into the box? How many wires are in each and how are they connected?

 

Sorry is the box the switch(dimmer) or the wall? The switch has a green,red,red,and black cable coming out of it. On the switch theres a green and red cable together. Also on the switch is a red and black cable thats together coming out of the switch. From the wall there is a copper,red,black, and black cable coming out. A total of 4 cables on switch and wall.

Its like this youtube video but the video is not clear on telling me which red cable to use for the wall cables.

How to Install a 3-Way Lighting Dimmer - YouTube

I will also attach a picture of my wall outlet. Sorry its not clear cause I had to use flash to take the picture.

I havent bought the new dimmer yet.

 

The box is the box in the wall. There are no cables entering your switch.

I didn't follow this link. Anybody can post anything on YouTube, and it's not a source I turn to when I want solid advice.

If the instructions that come with your new dimmer aren't clear, post back with your questions. You might want to buy a copy of Wiring Simplified at the same time. It is an inexpensive and authoritative reference for this work.