do you mean to perform the WB in a gel that was already stained with Instant blue?
i never tried but i do not think that it will work, since even if it is possible that the bands will be transferred, those bands are covered by the blue and i do not think that this will allow the binding of the primary mab that is required to detect the target protein in WB.
however in case i'm wrong, and it will work, let me know, that is it good to know!
Manuele Martinelli I think, Blue dye doesn't interfere much with the antibody binding. I have done western blotting from Blue native gels (non-fixed gel) several times and it worked fine.
Here, the problem is protein precipitation and fixation as Didier Poncet mentioned.