I've been tweeking the theme / color preferences in the Terminal.app a bit, after a while I found that when pressing a diacritical mark/accent/dead key there's a highlighted yellow rectangle showing a preview of the accent you're inputting. Here's an screenshot:

It turns out is not editable from the terminal preferences. In fact it seems like a system wide setting.

But it IS incredibly annoying to guess what it is displaying with a dark background + lighter text color in the terminal app:

Is there anyway to change that yellow color to correctly read those symbols no matter what text/background color is?