Is the discoloration on my bed frame rails mold?
This was already answered hours ago by another one of our more experienced users, when you asked this under a different username: 

Is this mold? Black? White?

Honestly, it appears to be simple iron staining. Appears black on wood, white on zinc coatings. Simple reaction of carbons in the metal and tannins in the wood. Although it is activated by moisture, it is not a mold, nor harmful.