There are a couple of things here you can try...
OS System preferences
The system prefs can allow you to change the highlight colour
What I often do is set the field fill colour to be the colour I want the highlight to be and then use a custom formatting of "True" and fill white. When the field is inactive it is white and then when clicked in it turns to the fill colour I had selected.
There are a lot of things you can do with custom formatting
One other thing to check is if you have the "Select Field Contentes" option enabled on the Inspector the text can be difficult to see depending on the highlight colour selected. Black text with a dark highlight for example.
Thank you very much. I have been messing around with conditional and it definitely seems to be the best bet. Thanks again.