I think only iron rusts. I think rust is a very specific name for brownish red iron oxide. But other metals oxidize, too. I think copper probably forms a blue oxide. Brass probably has some copper in it and can probably form a blue oxide, too. I tried on the internet for 'oxide blue chemistry' and found out that cobalt oxide - CoO - is used to make blue colored glass. Copper oxide is probably more green than blue. There are also more than one different oxide for some metals, and sometimes the different oxides form at the same time. For example, iron ions can have charges of +2 and +3, so they combine with different numbers of oxygen atoms when they oxidize.

Rusting is the process of Iron metal coming into contact with oxygen, usually from water, and binding to that oxygen to form a new compound, Iron Oxide...more commonly known as rust. Chemically, we call this oxidation-- the iron metal (Fe) is being oxidized to iron oxide (Fe₂O₃). We notice rusting because this oxidation is a very favorableprocess for iron. But all metal can become oxidized in the right conditions-- high heat, high oxygen concentration, high pressure, etc. We just don't notice because most are not favorable reactions at ambient conditions (room temperature, normal air pressure, etc).

Many brilliant colors of "rust" are possible, however. Different metals react in different ways. For example, copper can rust into a black material (copper oxide). But to do that, it must usually be changed into copper hydroxide by chemical reaction, and then heated.

Some others metal oxide colors: Cobalt oxide is a grayish-black powder that is used to produce a blue glaze in pottery. Lead oxide is yellow, and was once widely used in paint-- though the toxicity of lead has mostly ceased that practice. Tin oxide is blue/black.Gold oxide is brownish-black. Nickel oxide is black. Zinc oxide is white