TAdvMetroTile - transparency woes

I am trying to get a TAdvMetroTile to display picture from an imagelist:

if ImageList.GetBitmap(123, B) then   AdvMetroTile1.Picture.Assign(B);

It just wouldn't work with PictureAutoColor = True - I would get a solid white square in place of my icon. I did some more test with direct loading of files (which is unusable for me in real application, but OK for tests) and found out that this works (produces an icon which changes its colors):


And this does not (produces a solid white square):


My questions are:

1) Why - what's the difference between a .bmp and a .png that makes TAdvMetroTile render it differently?

2) Is there any possible way to get TAdvMetroTile to display an icon from an imagelist with PictureAutoColor = True?