Why are steam engines black?

[Trimetwes Fan1003]

there's one thing that i never understood, and that's why almost all steam engines are painted black? 

[T3G]

I would assume that they were painted black to hide soot and grime better.

That being said, this question is also heavily region-specific. If you are a fan at all of British Railways or their predecessors you may notice that they never shied away from painting their locomotives in bright and vibrant colours, reserving black/grey/etc for freight locos. The notable exception to this was during WW2, when locos were painted black to make them less visible to enemy aircraft.