Epilogue?
Exposition
Epitome? (It was mentioned in the Kids in the Hall sketch…)
I’m thinking of Monty Python
Symbol?
Resonance?
Seems to be simply a metaphor according to this description. Some More discussion points.
Pastiche?
How about leitmotif?
The phrase is usually used with music, but film theorists will use it for film imagery, themes, etc. as well.
I just want to double check that you saw Weirofhermiston’s suggestion of metonymy.
Semiotics?
Well then I got nuttin’. Please, please come back and tell me when you figure it out. This is going to bug me. 
Gotta be symbolism
Synchronic, even if inaccurate?
Explication, juxtaposition, mise-en-scene, goddam I hate these kind of threads. 
Reconsider “allusion.” The pool water being blue is an allusion to the blue meth.
Breaking Bad? Figures of speech? Sounds like you need a periodic table.
Former film major here. I am pretty sure we’d just say “visual metaphor,” or use descriptive terms like “recalls”, “evokes” or “mirrors.”
Embodiment?
I don’t think that would fit the usage which the OP is describing. Metonymy specifically refers to the use of language, wherein one figure of speech is a placeholder in larger, on-going discourse.
Yes, that’s what this particular example is, whether the OP accepts it or not. (It’s not a metaphor or allegory, because those serve different rhetorically purposes from that of the pool image.)