1: normal emptiness - black, 2: second pic is colorfast affecting the empty track
Colorfast affects the "nothingness" of an event-free track with its settings. When turning up exposure for example, it creates a grey veil by bumping up the luminosity. Here's a more extreme setting:
I had the problem with colorfast spilling over before as an event FX, but one could usually get rid of it by placing it before the pan/crop in the chain.I can't remember seeing this in older V versions.
The other thing is that colorfast clashes with the LUT filter. When both are on at the same time, no matter where in the project chain, at one point the screen starts to flash yellow / green and then preview goes black until I restart Vegas.