A telephone wall jack typically connects to red, green, yellow and black wires that run through the walls to the location of the jack. The phone cord plugs into the jack.
Sometimes, phone line wire colors differ from the traditional color set. The standard colors match other options. Red wires are the same as wires that are blue or blue with white dashes. Green wires are equivalent to blue and white wires or white wires with blue dashes. Yellow and orange wires are the same. Yellow also matches orange with white dashes. Black wire corresponds to either orange and white wire or white wire with orange dashes.