Ha! I'm 31 and I still have a fairly prominent blue vein on my jawline and still get asked occasionally if I know I've got blue pen mark on my face! Have had it since I was tiny and often got told I'd accidentally drawn on myself all through school (all quite well-meaning comments, not teasing). I've gotten used to it and don't even really notice it anymore. I was told this is just because my veins are a bit closer to the surface of my skin...hmm, not sure how this works. Not so noticeable in summer when I get a bit of colour on my skin (I have very pale skin).