If you mean to disguise the blueness, try Flawless pink, it's Creative's camouflage powder. I also like to mix it with some of the Perfect Colour pink powder to make it a bit more natural looking and not so solid. If you get what Im talking about...lol!
u say your client has blueish nail plates, what colour is her skin tone?
i ask this because if she is only blueish on her nails due to circulation problems but has golden warm skin tones u might b better in mixing a TINY scoop of the yellow mozaic powder to the mix that layla mentioned , and possibly a TINY scoop of orange aswell.
this may seem extreme but the small amounts of concentrated pigmented colour can "warm up" the tones of the finished look.
if however, your client has cool tones to her skin then stick with the mix that layla suggested.