This is where the mysterious purple coloring could come in. It's entirely possible that over time, this phosphor layer has peeled away from the blue light, altering the color of the street lights ...

Purple Earth Hypothesis suggests Earth was once a purple planet. Early microbes used retinal, not chlorophyll, for ...

which can lead to more salt molecules in the atmosphere", leading to the light being scattered more prolifically and creating "more vibrant pink and purple colours during sunrise and sunset".