The most common use of the term Whiter than White relates to laundry and was often used in adverts from the 1950's onwards. It was aimed at housewives who sent their husbands off to work wearing a white shirt.

I did a quick trawl of the internet and I cannot find it relating in anyway to race.

A few years ago a Tory MP used an expression meaning
(I wont repeat it) getting down to the detail. Some people called for him to be sacked because it was a term relating to slavery. This was a reinvention and the Oxford English Dictionary said the term probably came from an old German expression they could find no evidence that it was ever a slave term.

So if Whiter than White is banned how about "In the black" meaning I am financially sound?

I hope that someone has a quiet word with the complainer and tells him to stop being a snowflake (or is that now unacceptable)

One more point