Fire Diamond is a card that has been printed 10 times in 30 years (and once in gold border, but we ignore those), and of those 10 times, there've been five different illustrations. All of them are a red hunk of translucent rock. Unless it's the Phil Stone version, for which we infer that it's red.
Sure, Fire Diamonds tap to make one red mana, and not every deck can use red mana. But we're not here to determine whether or not you should play Fire Diamond. We're here to figure out which of the five different Fire Diamond arts fit your personality the best. This is highly scientific and the results can be used on job applications and dating profiles.
Lars Grant-West