Can this junction box wiring be used for a duplex receptacle?

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Hi – this junction box was covered with a plug cover That had no openings in it, just a blank cover over the wall box. As you can see from the image we have two cables entering the box from the top left back corner, each cable with four separate thin wires inside the main cables. The colors are green, black, red and yellow. The wires are much thinner gauge than I usually seen for the other outlet boxes in my house.

Does anyone know if this wiring will work for a regular duplex wall outlet? Id like to have a outlet plug where the box is. What color wires would I connect to the outlet?

My house was built in the early 80s, Utah, USA if that helps. The people who lived here before me did not take very good care of the house and I doubt they did much custom work to it. I am the third owner of the house.

Thanks in advance for the help.