In a vacuum, all colors of light, including green light, travel at the same speed. The speed of light in a vacuum is approximately 299,792,458 meters per second (or about 186,282 miles per second). This value is often rounded to 3.0 x 10^8 meters per second for simplicity in calculations. This speed is commonly denoted by the symbol "c" in scientific equations and is considered a fundamental constant in physics.