It seems to be a problem with qt component. I saved a little screencast
with the issue:
I have tested all parameters of my qt theme and the hexadecimal number that
changes the background and doesn't belong to the background that gambas
I also attach another screenshot with xt7 program and you can see that
occurs the same. It seems to be a change in the new version because with
3.3.4 version all worked ok.