I think you are right. The least common eye color is green. The purple eye color is just a variation of blue. According to statistics, 2% of the population has green eyes. The reason for this fact is that the green genes are rare and random. Actually, the so-called green eyes have no pigment of that color. Unlike the eye color with melanin, the green color is an effect of Rayleigh scattering which means that particles smaller than the light wavelength cause the light to scatter. Green eyes are just common in Central Europe and some parts of Eastern Europe.
I think red or violet. When we take photoes at night or in poor light, we inevitably appear red eyes, which seems really horrible. That shall be one of the reason why the photoshop is so popular worldwide. In general, eye's iris pigmentation and light scattering frequency determine the eye color. Various eye colors can occur in different parent-child combinations due to the complex eye color genetics. Technical saying, it is impossible for human beings to have blue or purple eyes. As a rule, we can see blue-eyed siamese cats and jungle crows. In fact, those colors may be a sign to indicate the pathological changes when they exist in human body, like albinism etc. Some Americans have blue eyes just because of the light scattering making it look like blue, especially for lighter-colored eyes. By the way, I favor amber eyes. Have a good day.
I don't consider purple or violet as an eye color as it is a variation of blue eye color. So does grey. Grey eye color is also a variation of blue eye color.
What makes blue eyes?
There is no blue pimentation in blue eyes, but the blue color are due to the Rayleigh scattering just how the sky look blue.
But green eye color is different as it has different type.
Green eyes are dut to the mixture of the amber and light brown pigmentation.
Therefore, I consider green as the least common eye color.