Middle Click Window Background

[ztyh]

Sorry if this is the wrong place (please direct).
This is freeciv 2.5.1 gtk3.
On my archbang OS. The window of the middle click is black and the letters are also grey.
This is a bit hard to see.
If I want to fix it so that the window is not black, where do I go?

I tried changing the gtk theme and openbox theme but that did not affect the window background color.
What implements this window popup on middle click?
So I know what to tweak.

Thank you very much.

[cazfi]

What is your gtk3 version? I've seen that problem with some versions of gtk3, but so far only in Windows, never in Linux.

[ztyh]

What is your gtk3 version? I've seen that problem with some versions of gtk3, but so far only in Windows, never in Linux.

It is gtk3-3.18.5-1.
I forgot to mention, I am able to change the letter color of the box.
But obviously when I change the letter to white, the middle click window is visible fine,
but then other parts become hard to see.

[ztyh]

If it is gtk, I guess I will wait until things get updated. In a dark room, grey on black is still legible. Anyways, thank you for responding.