Sorry, this picture was taken with my iphone.
On my Eotech XPS3, I noticed that there is mold/corrosion? on one of the metal screws. I picked off most of it with a knife, as you can see from the picture where the mold/rust developed. I am curious why it rusted. I've used this sight only twice. I do keep this particular AR in a pelican case, could it have had some moisture in it? But I have kept many of my guns in the same case for years and never had a problem with rust or discoloration.
The rust is an olive/greenish.