Cleaning Silver Slaps

So, my bass (Engelhart) was restrung with Silver Slaps about two months ago and I've noticed some significant color change in the strings. They seem to be fading to a "gut gold" kind of color over the fingerboard, are getting quite dirty over the playing area, and are snow white close to the bridge.

Before I start, I had a couple questions:
Is this normal? Is snow white even a goal worth working?
How do I remove the plucking gunk from the bottom of the strings without bashing up the finish? With metal strings, no problem, but I'm not sure if the same cleaning techniques would even work on the plastic-y surface.

 

The strings look like plastic wraps over some braided nylon or something. I'm pretty sure it's at least partially on the surface 'cause I can scratch some off of the underside of the E string with my fingernail.

I'm afraid for the smoothness of them, which I adore. Never had anything but metal before though, so who knows really.