It was in an article for beta 1 I think (I'll try and hunt the link out later)... It may have referred to the change in some stock icons (as in they've adjusted the white point... not 'you can adjust the white point') ...
UPDATE:
"Accessibility: A New option has been added in the Accessibility's Contrast menu, allowing users to reduce iOS 7's white point. This feature joins both the "Button Shapes" and Darken Colors options that were added in an older iOS 7.1 beta."
From:
https://www.macrumors.com/2014/01/07/ios71-beta-tidbits/
I'm just interested in if it actually went in, and what adjusting the white point actually does for adjusting the contrast... As in, could I wash out the bright icons by playing with it