Difference in base flares?

I have noticed that are 2 different colors of the base flares, but I can't figure out what why. There are some that are dark gray, almost black, and some that are very light gray. I know that some get faded and look gray, but that's not what I am talking about.
These are the dark gray flares:

https://inlandempire.craigslist.org/cto/d/wildomar-toyota-tacoma/6984888294.html

Then there are these:

https://losangeles.craigslist.org/sfv/ctd/d/north-hollywood-2006-toyota-tacoma/6987868279.html

They are clearly very different shades of gray and I doubt they would all fade perfectly like that, also there are many trucks I see with the light gray flares.

 

Tough crowd

 

there is only one dark black... the others are just faded.