Color-Changing Alexandrite & Fire Opal in 925 Sterling PendantThe color change effect is due to Alexandrite transmitting green and red light equally. Incandescent and daylight light sources are richer in different wavelengths (red or blue and green respectively) and this has a direct effect on what colour the gemstone appears to the human eye. Since the discovery of Alexandrite, it has been believed to bring good luck, good fortune, prosperity, and abundance. It's considered to be a very positive omen.