We are getting another phone line in kids room how do you rewire the jack

The phone company will connect the new line to the black and yellow wires at the interface outside. Somewhere between where the lines to the 2 phones split off and the new phone, you need to connect the yellow and black to the red and green to the new phone. I think it is yellow to red, and black to green, but not completely sure. Dig back in this forum a couple of week ago, and I think there is a similar question.