Well done.
Those blue lanterns were a good choice for a few reasons:
1. They appear more organic/alive than their surroundings
2. They are light blue beacons in the dull and depressing slums
3. If this were to be turned into a videogame, those lanterns are already a visual cue for players to pick up on. [Eg: follow waypoints/markers etc.]
The young couple still retain some color, but not enough to make them stand out too much - they seem very much apart of the slums, as if they're tainted/influenced by them.
All in all great job. Oh one thing, did you purposely place a lantern as a focal point above the characters to reveal them to the observer faster? It seems as if they're looking at the second lantern farther off.
Lantern, kids, farther lantern. Seems like a design pattern to me. Oh well I don't know just speculating. :D
Keep the good work coming!