Here is the designer mode, Thanks!
Thanks for the Designer mode screenshot. you are actually right in saying that you dont have an option in styling!
I was kind of wanting to suggest to style based on the currentSelectedObject but there isnt any such thing in the options too.
So the only option left to you is to go a CSS way. Check this question/answer: https://forum.mendix.com/link/space/app-development/questions/8860
Might give some help to you.
FYI: using the CSS attribute value selector you then have to style its Sibling. However this being mendix DOM, it may not be very easy to select a sibling directly. Check the forum post i gave above, it has suggested a method.