Make sure your saving your bmp as a 32 bit depth and not 24. that was where i had magik pink issues...

it also depends what your skinning too, sometimes only magik pink works...sometimes only png works....

try not to waste yr attention of how it looks in skinstudio.... for example my spinbuttons have an arrow glyph. png files left them with white squares after they were applied to the skin, so i naturally changed them to bmp and magik pink..... in sk they had hideous pink squares around them despite me checking transparency, but after i applied the skin in wb, it worked out fine....

so i guess its also a bit of trial and error and just time......