Problem with background colour in Fillable Text Forms

I'm having problems adding fillable text fields(boxes) to a PDF in PDF Architect Pro. The doc was originally created in Word (without the text fields). I can create the boxes under Edit and Forms>Text field no problem and if I right click on them edit the box outline weight and select the background colour as either white or no colour which is what i want. I can also write in them so text size can be selected too. Problem occurs when I save the pdf then call it up again. All the text boxes are suddenly filled in charcoal grey as background colour If I write in them and save them again when I open up they are still grey so it isn't a temporary "Write here" prompt. Can anyone help please? Thanks in advance!