Hi Karen,
Try to persuade your employer to move into this decade and use Content Controls. The protection needed to use legacy formfields is extreme and can make documents much harder to use. Mapped content controls can provide a very easy way to repeat information throughout a form. There are free tools available to convert a form using legacy formfields to Content Controls.
As far as I can tell, there is no option you can change for the color of Legacy Formfields. The Color options under the Design tab do
not change it and trying may mess up other color settings. Those are Theme color settings.