To see a stoplight in your dream suggests that you feel you are being held back from pursuing your goals. Your forward progress is being controlled by someone or by some outside forces. In other words, you are not in control of your own life. Alternatively, the dream represents the pressure to succeed or else be left behind. If the traffic is green, then it indicates that you have been given the go-ahead to follow whatever path you have chosen or whatever decision you have made.
To dream that you are running a red stoplight indicates that you are doing something despite being told not to do it. You are going against the rules.