“New” red area - do you have ones that have been present for some time?
Redness most often is an indication that the skin is being regularly irritated by what it is in contact with.
This can quite literally be anything from soap and shower gel, to whatever it is that your clothes are washed in.
Change, and therefore newly markings / patches / areas of redness are most often caused when a change takes place, such as using a soap, shower gel or other body wash that you have never used before, or as I say, less often you will get the same reaction when washing powder, or whatever your clothing is washed in is changed - and this is most often the case when a much cheaper product is used.
Then, some males actually masturbate in the shower or bath for example and use something like hair shampoo as a kind of ‘lube’ to masturbate with.
Penile skin, particularly the upper-shaft, foreskin and glans / head of penis is much more sensitive than skin elsewhere on the body and things like a relative high-concentration of any form of body wash is simply to much for the skin to deal with.
In terms of masturbation you would need to consider: the amount of time you masturbate each session, the amount of force / pressure / friction that is present during the time you are masturbating.
Then there is the regularity: several times within a 24 hour period, for example, or simply masturbating everyday does not allow the skin of the upper part of the penis to repair itself.
So, presuming there is no external cause of your redness - such as what I have described - it would be best to use something like Liquid Coconut Oil for skin as a lube that you apply before masturbating. A very light coating is all you need.
From what I describe and detailed which do you think may be happening for you … ?