Depends entirely on the printing method and the quality of the ink used. You can get white cartridges for some inkjet printers, but they certainly aren't opaque enough. ALPs allows for an acceptable opacity. There are also some sublimation printers which give a suitable whiteness, but of course these are rather prohibitively expensive.
This was done with decals designed by me and printed on an ALPs printer on clear decal paper. Yes there is a little colour shadowing, but it is minimal and more obvious in the yellow than the white.

Similarly designed by me and printed on a different ALPs printer. Zero colour bleed visible in the white over the dark blue. The comparison is easily made in the boundary.
