How do I change the color in Terminal indicating the use of a dead key?
This isn't a clean fix, but here's a work around:

Keep the Terminal as Black on White but then go to:

System Preferences &gt; Accessibility &gt; Display &gt; Invert Colors


Doing this will change your Terminal (and everything else) to White on Black, but also change the yellow dead key to blue.





You can also turn Invert Colors on and off using a keyboard shortcut if you turn it on in the keyboard preferences: