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.
The most obvious way is to put it in an incubator. and see if there is any growth. However, this is not the. most practical way when you are selling eggs for human. consumption. In that case, the best way to tell a fertile. egg is to examine the germ on the egg's yolk to see if. it has divided. The germ is also called the Blastoderm and is. where the baby chick begins to grow. The germ is. located on the surface of the yolk and appears as a light. spot.
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.