Night vision on white linen is still green
Taking this line literally, night vision goggles that allow people to see in the dark generally make everything — including something white like linen — look green.
Another interpretation is that the “night vision” Lu’s talking about is the vision of drug dealers and prostitutes who typically work at night. They see “green”, as in making money is their only concern. Furthermore, U.S. banknotes are made of a cotton/linen blend — check out how they’re made here.
Lupe’s also playing on the homophones night and knight, linking this line to the previous one and making reference to the Knights Templar. Check the annotation above for more. The Knight Templar vision is on green paper, i.e. money.
To help improve the meaning of these lyrics, visit “Peace of Paper/Cup of Jayzus” by Lupe Fiasco Lyrics and leave a comment on the lyrics box