For the past 7 months or so I have noticed areas of deep purple coloration on the head of my penis. The colour seems to vary depending on temperature and with the amount of blood that is in the penis and is also more visible under different types of lighting. The patches are all around the coronal ridge and appear more prominent and seem to look more like spots on the left side. They do not appear to be raised. I have also had pain in glans which initiated the regular inspection of the area and led to the discovery of these patches. The pain tends to be sharp and lasting only a few seconds but at times it has also felt bruised. The glans as a whole has also been quite sore throughout. I have seen my GP who couldn't see a problem but did routine urine and blood tests and I have also been to the GUM clinic on several occasions and tested negative for STDs (urine & swab). They gave me treatment for thrush on 2 occasions which only seemed to make the glans more inflamed and had no impact on the purple areas, they then prescribed a soap substitute emollient (diprobase) which has also not helped.