Pencil Stains on TPU overmold!

Hello! I recently noticed that on the sides where I rest my hands, the blue TPU overmold has discolored greyish. I have already tried alcohol and some water, but to no avail. Anybody have tips? Thanks!

I would try with putting glue on and then peeling it.

Hot glue doesn’t seem to stick too much to the plastic, and also maybe PVA could be less agressive.

I will try that! I have another suspicion that the grey may be apart of another color bezel from the manufacturing proccess, (this could be completely wrong). I do also have an ultra sonic cleaner, but it is quite a lot of work to get the bottom out.