Rubedo is a Latin word meaning "redness" that was adopted by alchemists to define the fourth and final major stage in their magnum opus. Both gold and the philosopher's stone were associated with the color red, as rubedo signaled alchemical success, and the end of the great work. Rubedo is also known by the Greek word iosis.
https://www.youtube.com/watch?v=3kPi0JqvRRs 