How do I keep a white dog white?

[parklives]

Seem to have acquired a dog (after many months looking at every rescue charity in the country!)
He's white, how does everyone keep their dogs white, rather than orange around their mouths, paws, groin ?
There seemed to be loads of expensive products out there, but all with mixed reviews.
Anyone got any recommendations?

My last dog was white and she was also self-cleaning. Back from a walk, if I wasn't quick enough washing the mud off her legs, she would set to and lick it all off herself. My current dog is brown and white and she, too, cleans herself up. Just lucky, I guess

Purple shampoo.
Don't leave it too long, unless it's a poodle like departed Wisdomdog in which case they like being purple.