An Interesting Discolored Ffarquhar Station

[Super]

All interesting theories but I can't help thinking that the green windows/doors and the stickers especially that white one are not affected by whatever this is. Plus if it were affected by these theories wouldn't we have seen others over the years with similar discoloration?

Now I am leaning towards it being a modification as I think one could remove the green window/door/sign and seat then apply some type of brown wash or something and replace all. I am half entertaining the thought of buying this to investigate further.

@Chrisjo
Do you still have that fantastic Custom Station you made out of 2 of these Ffarquhar buildings?