The color of sky is blue due to the molecules in the air dissipate blue light from the sun more than they dissipate red light.
This disease in particular is an STI known as Gonorrhea. Gonorrhea is a bacterial infection caused by unprotected intercourse. More of less one of the more locally painful STI, which does cause discomfort in the genitelia, as well as discharge, and discoloration. It is luckily a curable STDs, usually with antibiotics.