Generally speaking, “olive oil” is simply the oil that’s obtained from the fruit of olive trees. In itself that sounds pretty simple and straightforward.
But there are different varieties of olive oil that are set apart not by the type of olive that’s used, but the process used to extract the oil, as well as by the additives, and the oil’s level of free oleic acid.
Looking at this particular brand of olive oil and extra-virgin olive oil side by side, you can see that the extra-virgin olive oil has a noticeably darker color, while the regular olive oil has a lighter, brighter hue.
This color differential, however, varies from brand to brand, and it is deceptive. You cannot use color to reliably tell two grades of oil apart. Olive oils can vary drastically in taste and quality, and color is only one factor and not the distinguishing one.