RED light occupies the lower, longest wavelength, segment of the visible spectrum. The color red penetrates the furthest through any particulate matter suspended in the air like dust, smoke, and water vapor. Red thus preserves night vision . Orange light is next up from red. The eye is a tad more sensitive to this color, but it also has more effect on night vision.
Yellow light is next up the spectrum from orange.
Yellow penetrates almost as well as red, and the human eye is more sensitive to it. It does interfere with night vision, but not as much as shorter wavelength colors, so it is usually a good compromise between penetration and visibility. This is why automobile fog lights are typically yellow. Green light is right in the middle of the visible light spectrum. The human eye is the MOST sensitive to green light.