A typical inaccuracy in human sight is the left-right deviation (also known as “The Master Eye Effect”). Generally one eye is stronger than the other creating a slight color deviation in one’s perception. A stone placed to the left will appear slightly darker than the same stone when placed to the right (it may be the opposite case with you, depending on which of your eyes is stronger). For example, when the stone in question is darker on the master’s left and lighter on the master’s right, it should be a match in color. Be aware that these color variations are very slight. As you gain more experience in color grading, you will understand how slight the variation is, by seeing how little the color changes from one grade to the next. A very common mistake in buying is looking through those proverbial rose-colored glasses. A buyer must be very cautious when color grading, to make sure the purchased diamond is not a regretted decision. Make sure your eyes (and mind) are well-rested and alert. Make sure your light source is filtered, cool white, balanced fluorescent bulbs. The advantage of this type of light fixture, unlike natural sunlight, is its lack of ultraviolet light, which affects the apparent color of an object.