Yes..I agree with PhotosGuy.... Your shots are great... (Paris.. What a lovely place to shoot).. Plus.... a slight glow in the sky really helps. Whenever possible, I try get a glow on the horizon. Black skies are kind of flat and sometimes pick up the tint of the surrounding lighting...
To get the effect, sometimes I'll go to a spot early and just sit for a while until the light is right. Also.. Most cities are lit with those cost effective, mercury free, highly efficient, but HORRID looking sodium vapor lamps.. These throw a very orange cast on cloudy skies.. I find a cloudless evening is the best.
I usually choose tungsten white balance to minimize the orange cast.. Or, I'll use the RAW white point eyedropper to select a white point in the scene.
Here's one I did last week that shows the blue glow sky effect......
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