My 11 year old son brought it to my attention twice this weekend that he had visible veins on his chest and thighs.  I noticed both times were after he showered.  He is good health, has no other symptoms.  But veins were very visible and blue. He is not fair skinned.
Hi...nothing to worry about. This is a very common condition and this is called status marmots and the skin of fair skinned individuals shows this response for changes in ambient temperature and while taking bath due to the temperature changes in the water. Nothing to worry about. Regards -