Text Box and Math region background colors can be applied using the color picker dialog box. However the limited number of solid colors are not augmented with a opacity slider as we had on Mathcad 15. This is important because our legacy documents had various colors for input variables and math result fields which cannot be reproduced in Prime 7. Also most of the solid colors available when printed are simply too dark make the black text unreadable.
Please consider an opacity slider as we had in Mathcad 14/15. see attachment.