HIghlight in menus

I’m sure there is a way to do this, and I’m sure it’s tucked into the theme editing options somewhere, but I can’t see it and it’s beginning to drive me a little ga-ga.

Essentially, I’m using the ‘Solarized Light’ theme and I love it for the most part - until we ever (please!) get the option to change the editor background to a tileable texture like, say, hand-made paper - but my problem is that the highlight that applies to items when you’re working through menus is defeating my colour-blindness and I can barely tell what it highlighted and what isn’t.

So the $1m question is - can I change that? If so, how?