Simply because color is not a quality attribute of extra virgin olive oil. As a reminder, the sensory attributes of extra virgin olive oil are fruitiness (on the nose), bitterness (on the palate) and pungency (at the back of the throat).
Thus, when an olive oil is evaluated in quality competitions, the jurors taste in blue (or red) glasses so as not to be influenced by the color. For this reason, you will see that some brands highlight them or offer you tastings in these small blue glasses.
For your information, this blue glass is fully regulated by the IOC (International Olive Council): its color hides that of the oil and its shape allows the best possible tasting (and evaluation) of extra virgin olive oil.
Personally, I offer tastings in transparent glasses, because as a consumer or chef, pleasure also comes from the eyes or the decoration of a dish.
