How could I do this with transistors?

I quickly threw together an ethernet tester today, but I want to make a really good one too. I want to have 2 LED’s for each wire, one red and one green. When I turn on the power I want to have all the red ones lit, then if the circuit is completed they switch to the green. Is there a way to easily do this with transistors?

basically use them as mini relays to that if the positive from the ethernet line comes through then it will turn on the green led instead of the red led.