The color of the Olive Oil depends solely on the maturation stage of olives (for this purpose we must say that all the olives are black, if you let them fully mature). When green, the predominant pigments are chlorophyll and, the more the olives mature, more chlorophylls are being replaced by carotenes and xanthophylls.
The natural color of the oil depends only on the relative percentages of these types of pigments that make the Olive Oils green, at the beginning of fruit maturation, and with advancing aging change their color until they are completely yellow.
Regarding chlorophylls, it is important to know that these chemicals compounds have dual behavior from the point of view of oxidation of the oil. In the dark, they behave as antioxidants and under the action of light behave otherwise function as pro-oxidants. The knowledge of this fact is important, for example when choosing the glass container to be dark in color.
The Olive Oil’s green color is associated with a more intense fruity aroma and flavor, with more evident notes of bitter and spice because it is an Olive Oil more rich in antioxidants, particularly polyphenols. More yellow oils are smoother but less interesting from the point of view of sensory experience.