using the formula for changing the wavelength of the Doppler effect, you must consider how the color of the light emitted by the Sun changes as we approach it and as we move away from it, as the Earth orbits. I remind you that we are only interested in the change in the maximum radiation of the Sun, that is, you only need the color green. You will need data on the speed at which the Earth moves in its orbit. In the same way, try to calculate how fast you need to move to a traffic light to start looking red as green.