You can change that with qt5ct.
[ColorScheme]
active_colors=#ffffffff, #ff383838, #ff2d2d2d, #ff343434, #ff2d2d2d, #ff353535, #ffffffff, #ffffffff, #ffffffff, #ff282828, #ff2d2d2d, #ff000000, #ff1a9c82, #fff9f9f9, #ff11cba3, #ffa70b06, #ff2d2d2d, #ff2d2d2d, #ff343434, #ffffffff, #ffadadad
disabled_colors=#ff808080, #ff383838, #ff2d2d2d, #ff343434, #ff2d2d2d, #ff353535, #ff808080, #ffadadad, #ff808080, #ff282828, #ff2d2d2d, #ff000000, #ff1a9c82, #ff808080, #ff11cba3, #ffa70b06, #ff2d2d2d, #ff2d2d2d, #ff343434, #ffffffff, #ffadadad
inactive_colors=#ffadadad, #ff383838, #ff2d2d2d, #ff343434, #ff2d2d2d, #ff353535, #ffadadad, #ffadadad, #ffadadad, #ff282828, #ff2d2d2d, #ff000000, #ff1a9c82, #ffadadad, #ff11cba3, #ffa70b06, #ff2d2d2d, #ff2d2d2d, #ff343434, #ffffffff, #ffadadad
Put this into a colorscheme file (@bogdancovaciu knows where, I forgot) so you can select it. Then, install qt5ct and activate it like this:
QT_QPA_PLATFORMTHEME=qt5ct
Or something like that. @bogdancovaciu knows better and I’m not on my computer right now.