learning a new word: phthalo

[disassembly_rsn]

phthalo in this context - as a modifier for 'darkness', referring to the evening sky - appears to be short for 'phthalocyanine'. According to wikipedia, 'Phthalocyanine is an intensely blue-green coloured aromatic macrocyclic compound that is widely used in dyeing.' According to AHD, the word covers several blue or green organic compounds used in enamels, printing inks, linoleum, and plastics.

I admit to doubt as to whether the viewpoint character would know this word.