Pup color

[Sarah Conte]

Hi all
I have a two week old litter from Pepper Anne (spotted Lilac) and Puck (PEW).
 They seem to  be three Argente Creams, a spotted Dove, and a spotted either
Red Fox or Argente Cream.  I don't know whether she's a Red Fox or Argente
Cream 'cause she would have a white tummy regardless, since she's spotted.  
Does anyone have another way I can determine this?
Thanks,
Sarah