Most of the cyanosis under the eye is due to the color of the choroid, especially the choroidal vessels, which are seen through the thin scleral tissue here. It is usually observed clinically and presents mainly as irregularly shaped greenish-gray, or grayish-brown and dark black irregularly shaped stains above or below the white of the eye. This condition occurs at birth but does not change much as it grows, mainly due to the color of the deeper tissues seen due to the thinner sclera. It is usually not treated clinically and there is no good way to deal with it. It does not affect vision and is not painful or itchy, so it is mainly observed and followed up. If you feel significant pain and have poor vision, you also need a fundus examination, especially in small children, to rule out congenital developmental abnormalities.