I believe it is Epithelial Tissue. <span />
Red Orange Yellow Green Blue Indigo Violet
<---Longest wave length shortest wave length--->
As you went down the colors of the rainbow the wave length got shorter or faster.
A cat thinks that you are opening a can of cat food when it hears the can opener.
A dog shying away from a magazine or newspaper, if the owner has used one to swat the dog as punishment.
If humans are ok to use as examples, A child learning that a stove is hot by touching it.