This is additive color. Red, green and blue are the primary colors of white light. All three colors will result in white, the absence of all three will produce black. When two primary colors of light are added together, you get a color that is brighter than either of its components.
MYTH: A blood spot inside the egg means the egg is fertile. FACT: A blood spot inside an egg can occur at various points in a hen's reproductive system as a result of a blood vessel rupturing. It can be the result of a genetic predisposition, a vitamin A deficiency, or a random event.
Eggs are usually fertile from about week 7/8 a week or two after the females start laying as long as they have had males in with them. It is a good idea to give the femal and males a week together after the hens have started to lay before you take the eggs for incubation.