So after letting my car sit for a few years, I've started fixing things by working in the back first and working my way forward.. So with that said, I'm currently working on restoring my tail lights and am looking for a little guidance and possibly some suggestions on how to handle this.

On the passenger side clear reverse section, I have this rust colored stain on the plastic..



As you may or may not be able to tell by the haze on that spot, I've been wet sanding it with 600 grit and its just not coming out. I don't want to go too crazy with sanding it down to prevent any other potential issues. it is 100% on the outside. I've done some searching on the topic and couldn't find any similar situations, so I'm hoping someone might have a little helpful knowledge on this. The easy way out would be to find another passenger taillight, but other than this discoloration it's a very solid light to restore and make look better than new.

I am planning on using some red and amber tint spray to make the red more red and the amber more amber.. I've toyed with the idea of using the red tint spray on the amber section as its a nice clean look when done, but would rather keep the original styling of it. As of right now unless I'm able to get this mark out, I may feel compelled to use the red tint on all of it but would really rather not if I can avoid it.

Also, is it best to use the tint spray from the inside or outside?

Lastly, I'm curious what others might be using to seal up the lens to the housing

Any help or suggestions are greatly appreciated. Thanks in advance.