The background buildings have a cyan cast – this is easy to fix. Generate a selection from Alpha 5 and hit Cmd/Ctrl + U to access the Hue/Saturation slider. Next, use the Edit menu to select the cyan; adjust this to -85. To add more contrast to the entire image, duplicate this layer, set the blending mode to Multiply and adjust the opacity to 30 per cent. Now select Merge Down, naming this layer 'City'.
Open Sky.jpg and drag it into your Photoshop document, positioning it beneath the 'City' layer. Name the layer 'Sky'. By using the Free Transform tool while tweaking the warp and perspective, you’ll add a dramatic look to the composition. Next, clip a levels adjustment layer (see Tip Box, right), setting the midpoint slider to 1.19. Clip a colour balance adjustment layer, setting the red midtone slider to +12 and the blue midtone slider to +26.
Delete any white halos on the City layer (Layer > Matting > Defringe by 1px). Continue with any colour adjustments to blend all the elements together. I changed the Hue/Saturation of the foreground buildings by using Alpha 3 as a selection, setting the blue’s saturation to -27 and Lightness to -7.