Luminous Landscape had a strange story about this paper's colour - http://www.luminous-landscape.com/revie ... tale.shtml
As well as ink, the colour depends on how much (if any) optical brightener is in the coating and then what proportion of various UV, blue etc light illuminates the print. Unless you can completely control the lighting your print will have you need to use papers with no brightener, or put up with these slight colour casts.
With Hahnemuhle Photo Rag Baryta (not the same as FB) I've sometimes applied a minus magenta correction to diminish a pink/purple tinge in light grey areas seen in daylight. But it's no bother in any artificial light that I use.