You can get new stickers from CarBone in Poland.
Color is debatable. I think the consensus is that it should be some shade of gray. The brown/tan of most older tanks was not the original color. It aged.
See this thread:
https://forums.pelicanparts.com/porsche-911-technical-forum/942272-gas-tank-coating.html
I used Rustoleum Smoke Gray, with a brush. Looks great. Maybe a litttle too dark, but good enough for me.
Mark