i think colour works fine for this image, the blue in the skies is a nice, deep blue, and the photo is already a very simplistic, almost monotone--just black and blue and white, with almost no other colours already.
nice, clean, simple photo...i just love the colours.
I agree with fw007 ... the gradient of the sky is nice and there's quite enough contrast btwn the cranes' silhouette and the sky for most parts ... i think it's a nice take ... was there another angle for a shot of a single crane? - am trying to visualise if an even less cluttered shot would make a stronger pic ....