what is signal colour
Signal Colors and Their Meaning. The colors used in today's signals are green, yellow, red, lunar, and white (remember, we're talking about signals in North America). The color of a signal tells the engineer what he has to do, the location of that color, determines the speed at which he is allowed to do it.We will get to the speed thing in a minute.he colors used in today's signals are green, yellow, red, lunar, and white (remember, we're talking about signals in North America). The color of a signal tells the engineer what he has to do, the location of that color, determines the speed at which he is allowed to do it. We will get to the speed thing in a minute.