Magnesium oxide is white. Period.

Magnesium oxide - Wikipedia, the free encyclopedia

The metal, un-oxidized is, in appearance, indistinguishable from: aluminum.

(Excerpt from WIKI

Physical and chemical
Elemental magnesium is a fairly strong, silvery-white, light-weight metal (two thirds the density of aluminium). It tarnishes slightly when exposed to air, although unlike the alkali metals, storage in an oxygen-free environment is unnecessary because magnesium is protected by a thin layer of oxide which is fairly impermeable and hard to remove.

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