What is the product of mixing red light and green light?

Yellow light. They make a "tricolor" LED that glows red when DC biased in one direction, green when DC biased in the other direction and yellow when AC biased. There are only two diodes in it - a red and a green. When you AC bias this thing, both diodes glow and...you get yellow!
Yellow light. They make a "tricolor" LED that glows red when DC biased in one direction, green when DC biased in the other direction and yellow when AC biased. There are only two diodes in it - a red and a green. When you AC bias this thing, both diodes glow and...you get yellow!