Lishy Because any tint is changing the colour of the regions. As white, or 'none', is not an option, all other colors are changing the original region color because of this tint. Red is no longer red, but purple, yellow turns greenish and so on. Don't know if you use waveform with regions, but if you do, you know what I'm talking about. If not, maybe try it.
Don't get me wrong, ST4 is turning out great, but this is the last bit that disappoints me. Everyone seems to get buses, midis, codes, chords and all kinds of bells and whistles. But this seems to be too difficult. So for me, ST3 will live on. Fine.