There are only two different eye colors in the world: brown + blue.
brown is the most common
blue is the rarest
Iridology also recognizes another iris color: biliary. This is a mix between the blue and brown eye and is often assumed to be brown or hazel by the naked eye. This is my eye color.
Eye color is determined genetically.
The reason why there are seemingly hundreds of different iris colors and shades within those colors, is because the body has the ability to lay down pigments of all colors on top of the base color the individual was born with.
Green white yellow brown orange red black
Blue and yellow = green eye
Blue and white = gray eye
It would be a misconception by the observer to think that eye color changes. It does not change. It's a genetic trait. However, it does accumulate different colors in it, giving the appearance of change.
Look at the gorgeous array of colors in the iris above.
What is your eye color?