How would you describe the color of this rose? Would you say it's yellow, sort of lemon yellow, or maybe a bright canary yellow?
Your perception and interpretation of color are highly subjective. Eye fatigue, age and other physiological factors can influence your color perception.
But even without such physical considerations, each observer interprets color based on personal references. Each person also verbally defines an object’s color differently.
As a result, objectively communicating a particular color to someone without some type of standard is difficult. There also must be a way to compare one color to the next with accuracy.
The solution is a measuring instrument that explicitly identifies a color. That is, an instrument that differentiates a color from all others and assigns it a numeric value.