Probably artificial crystal, only artificial crystal can change color. Find a local jewelry appraisal agency and look at the hardness and refractive index.

If you are not afraid of breakage, try the hardness yourself. Scrape the glass with this crystal. Be sure to scrape the glass with a smooth round surface to see if you can scrape the glass. If the crystal is not damaged, it may be true. I just said "maybe" because many artificial gem are also very hard.