So, on the top, you’ll see the original photo. On the bottom is my edit. Now I’ll explain how I did it, so that you can also learn some good photo-editing tricks!
For the flying buses, I grabbed a photo of a monorail and removed the background. I covered up the logo and everything else. Next, I plopped the PNGs onto different layers in Clip Studio and adjusted the hue for each, so they were different colors.
To change the sky, I first had to use my trusty selection tools to erase the original so that I only had the cityscape left. I put this lovely photo underneath it to allow the city to cover up the mountains. In the scene where the backdrop shows up, the characters are standing on the roof of a building looking at the city, so it wouldn’t make sense for the water to be there. I cropped it out.
For the city itself, I adjusted the contrast to make the lights brighter and the darks blacker. My trusty airbrush tool colored different portions of the city, and when I switched it to transparent, I brushed it near the tops of the buildings to give them some of the color of the sky. This made the city look like it fits into the setting.
And voila! It’s done!