When I upgraded to Indesign 2017.1 the Check Spelling window has become practically useless because I can barely make out what is in the Not in Dictionary field.
How can this be corrected other than changing the Interface preference to a lighter color which I don't want to do? I'm running on OS 10.12.4 on at late 2015 27-inch iMac.
I totally understand the problem you are facing. This issue has also been reported by other users of InDesign CC2017.1
It seems like a legibility issue with the new modern UI.
I suggest you report it as a bug here Feature Request/Bug Report Form