Finding molecules in the street lights

 These streetlights on the seafront at Eastbourne made me remember the way that I used to draw molecules in class. Three atoms but two colours would mean only 2 elements in my scheme so this could be H2O

Here is a different arrangement. Ignoring continuity of colour scheme it could be CO2

The next one perplexed me. Could there be a molecule of 3 atoms but 3 elements as well? I had to look it up: HCN hydrogen cyanide!

Finally, the Belisha beacon could be any monoatomic element like the Noble Gases/