What version of FM?
Right click the field and select conditional formatting
Create a new conditional format "formula" with this expression:
Get ( WindowMode ) = 1
Select the desired fill color.
Thank you very much for your answer @PhilModJunk, I've already been helped out by some of your old posts! To be a little clearer I'd like to change the Field fill for when it's highlighted in Find Mode. Get ( WindowMode ) = 1 changes it when it's deselected however it goes back to White when specifically searching in that box. Thanks a bunch for helping though!