How do I fix this?

[Meadows11]

How should I replace this?

 

[markb5900]

Bathroom sink drain?
From the picture, it looks like an excessive amount of plumbers putty.
You can take a sharp razor knife and trim off the excess.

 

[norty1]

Does it leak? If not trim it with a small putty knife. If it looks like crap, remove it just like a kitchen drain and re-apply plumbers putty.

 

[JFlightRisk]

The kitchen drain baskets did the same thing after we bought it. I scraped the excess off with a plastic scraper and cleaned the residual with WD40. I also checked the tightness of the underside basket nut just to be sure it wasn't loosening up from the plumbers putty squeezing out. Did the same on the bathroom sink and tub drain.

What you have is fairly common from getting hot in the camper. The putty gets soft and squeezes out

 

[Tunce the traveler]

Plumbers putty should always remain a little soft so you should be able to remove it by just using your thumb. If not then I would recommend removing the strainer and replacing it (the putty). Roll it in the palm of your hand into a worm shape the length of the circumference of your strainer and tighten so it looks the same as what you have in the pic. Rub off the excess and your done for about 10 years

 

[craigav]

I would use a plastic razor blade (or similar) and the red area appears to be anti-freeze although I am not sure how to clean the anti-freeze stain. I don't think RV anti-freeze leaves a permanent stain and perhaps most cleaners would remove the red ring. ~CA