I noticed a dark blue vein across my 2year old eye lid above the crease 2Easters ago. It s very dark, noticeable. He still has it, about to turn 4. He didn t have it as a baby or in any pictures from the summer before that Easter (i was looking back throuhh up close photos from before I noticed it).
These blue veins are completely normal. Everyone has such vein but is more visible in some peoples due to the lack of excessive subcutaneous fat in the eye area particularly in infants, or if someone has problems with sinus infections or chronic upper respiratory infections or if the person has lighter pigmented skin. When a person experiences sinus infections or colds, these veins become more pronounced due to swelling.  The best way to deal with these veins is to wash your face with cool or cold water & apply ice packs to the eye area to reduce swelling by vasoconstriction. Laser surgery could offer some remedy for those who want to remove for cosmetic reasons.