Removing white film from M-button - I need tips!

Hi friends!

When I got my M8 a month ago there weren't a lot of cases available so I chose a very simple no name silicon skin. Now today I went to a Meizu Store and got myself a new Mofi-bag and a new screen and back protector. When the silicon skin was removed I realized that the M-button looked kind of ugly. It looks like if theres an oily film on it or maybe like it would be a little scratched.

I tried to use a small amount of alcohol and the cleaning cloth from the box but it didn't improve the button in any way.

I'm kind of frustrated because I always kept the M-button protected and now it looks like it has been used for 2 years and not for one month (the black is also much lighter than the rest of the phone now). Any ideas about what I can try to fix this?

I heard there is some kind of paste for scratches on displays... Do you think something like that would work here?

Thanks for any idea that could help me!

I would just rip that thing off, looks like protective foil or something to me.

I would love if it was that way but unfortunately it's not a foil... it seems to really be the plastic.