The problem I was facing is the opportunity to change the background in fields in a model driven app. Unfortunately, there is no easy way of doing that rather than implementing a PCF. The PCF in this solution allows to update the background color of a text field. Currently only the Multiple and TextArea are supported.
Import the solution into your environment. If you have a textfield inside your form - go to the components tab while you are in edit mode and use the MultilineColorChange component. If you cannot find it in the popup make sure to have a look in the search for more components tab. Once you can select it make sure to tick the show component on fields and add the two requested static values A rgb(xxx,yyy,zzz) value (For now only rgb works - no hex or hsl colors) A Number (Can be any Number - will get parsed to Int and multiplied by 2.5rem for the lineheight)
As shown below:
Apply the changes and you will see the color in your field.
If you encounter any problem or wish more extension feel free to message me via LinkedIn.