Some "whitewalls" are whiter than others. I know, I was a Rubber Chemist for Armstrong Tires for a lot of years. Depending on how much
zinc oxide, titanium dioxide, anti-ozonants and anti-oxidants it contains the white can be bright or off-white. BFG is not known for the money they put into whitewall rubber.
409 does a nice job bringing out whatever white is available. Use white chalk if you want to really get a bright white.
Bob