I made better versions. Plus you dont see green red and yellow at the same time lol
Green light: minecraft:white_banner{BlockEntityTag:{Patterns:[{Pattern:hh,Color:15},{Pattern:hhb,Color:15},{Pattern:bt,Color:7},{Pattern:tt,Color:5},{Pattern:mc,Color:7},{Pattern:cbo,Color:15},{Pattern:bo,Color:15}]}} 1
Amber light: minecraft:white_banner{BlockEntityTag:{Patterns:[{Pattern:hh,Color:15},{Pattern:hhb,Color:15},{Pattern:bt,Color:7},{Pattern:tt,Color:7},{Pattern:mc,Color:1},{Pattern:cbo,Color:15},{Pattern:bo,Color:15}]}} 1
Red light: minecraft:white_banner{BlockEntityTag:{Patterns:[{Pattern:hh,Color:15},{Pattern:hhb,Color:15},{Pattern:bt,Color:14},{Pattern:tt,Color:7},{Pattern:mc,Color:7},{Pattern:cbo,Color:15},{Pattern:bo,Color:15}]}} 1