TItle?

It's a great easter egg within the movie! But if you'd like to know, after the car wash scene, Alexandria gives the taxi driver a tangerine scented air freshener as a Christmas present, to mask the vomit smell from the previous passengers who threw up all over the car. You can see that there may be some symbolism with the types of day to day lives of these women trying to make their life better to try to make the stinking reality more bearable, and possibly even making the mixture of the tangerine flavor and the vomit leave an even more disgusting stench.

On the IMDb trivia, it says that the title of the film comes from the color of the Los Angeles sky at sunset.

ALL answers are correct. Heard the director speak about it. It simply is a title of a work of art. Like a song. Or a painting. Rare with films. It is interpretive.