i saw some different colour on one side of my pennis shaft and it reduces and when i mastrubate it becomes visible .i dont know wheather its because of mastrubation or the soap i use.
Okay, when you have a potential of something, such as the soap, easiest thing is to rule-out all soaps AND ALL forms of body wash, such as shower gel and do NOT apply them to your penis.
After urinating, sex or masturbation simply wash your penis with warm running water, best is when you take a shower, rub the head and upper-shaft area with the inside of your hand and fingertips to fully clean, then completely dry when you are out of the shower.
Photos are not always a true reflection of what you see in front of you but it would suggest you have a relatively minor pigmentation issue. These are very common and there are several conditions that can potentially cause this - all of which are medically unproblematical, in that they cannot cause anything that would cause concern.
So, you are in the current situation where there is a potential cause to the external skin - such as the soap you mention, however, this is most unlikely, but I would try the water only approach that I suggest for at least 5 to 7 months.
What you more likely have is what can be described as a ‘natural’ pigmentation change going on - I would suggest that unless you get a dramatic change, such as an area turns almost bleached white, it is unlikely you have a health condition, or a dermatological reaction that have caused this = natural pigmentation change is most likely the conclusion