Sorry i'm from Belgium and the only phrase i ever heard of such kind was something with a bird and a worm ^_^
I agree but partly.Somewhere it would make more sense, I mean Zapdos and Raikou are yellow and in my eyes that turbine looks more like a drill of some sort.
Also that hue i cannot directly find at the fire and electric group PoKéMoN, Houndour(+evo) and numel are the only one who are not truly orange or red yet houndour is of course primarily dark and still has a bit red and numel is part ground and looks like a vulcano.
Come to think of it who says that phrase exists in Japan?
Well, "white hot" has less to do with the phrase and more to do with scientific fact. In the case of stars, the hottest stars are white, and then descend the spectrum from violet to red, which are generally the coolest in temperature. That being said, "cool" is relative to those superhot white stars.
Also, flames can be any number of colors based on the substance in which they are produced. Flames produced from burning silicon are a different color than flames produced from burning hydrogen, sulphate, uranium, etc.
So, really, it's all largely irrelevant. Visually, most people would imagine red, orange, and yellow as being artistically related to the matter of fire and heat. But, in actuality, flames can span the entire visible spectrum in terms of which light they produce from incinerating a material.
As to whether any of this influenced the artists in their designing of Reshiram--I kind of doubt it. I find it more likely they just selected a type after designing the legendary which fit the theme of "Black/White". And instead of choosing a generic Normal/Flying or Dragon/Flying type, which is typical of such a generically colored design, they decided to be a bit crazy and make it a Fire/Dragon.