Text Field - Fill Color

I am developing a form with a drop down list and multiple text fields. Base on the user select on the drop down, other fields will be changed as Mandatory or ReadOnly

To improve the usability, i want to gray out those Not required / Read Only fields.

I am trying to do it with the following script:

this.resolveNode("textField1").fillColor = "195,195,195";

However, both caption and input box area are gray out.

Is there any script that will gray out the input box only?