Thunar root warning

[viniciusov]

I'm using Arc-Dark theme (with hdpi window controls) in Mx Linux 18 (xfce).
The issue is when I use Thunar (default File Manager), right-click on a folder and choose "Open as Thunar Root".
I get this yellow bar, warning that I'm running as root:

As you can see, it's nearly unreadable and I don't know how to change the colors (yellow bar or the light gray font).