I don’t know Arch or your DE, but purple is your OS’s accent color. perhaps the issue is not in qt5 but somewhere else like /usr/share/themes, ~/.themes or ~/.local/share/themes.

the composite last names of both the italians is typical of ancient, rich and maybe noble families, so at least for them it might be money.

Don’t you even try. The people voted the Tories, UK is not a dictatorship. We are paying the consequences of our stupidity.