On this page of the "Colors and line styles" dialog (which can be opened using the corresponding button in the toolbar at the top of the main window), you can set colors and fonts for objects that are not located within the diffraction pattern.
For most elements (like the "Restraints" or the "Additional entries" tab), the current color is displayed in the corresponding box. On the right-hand side of each color box you will find a button "Modify...". By pressing on the button you can open a color selection box where you can select/define a new color for the corresponding graphical element.
At the bottom of the "Others" page, you can define the font style and size for all dialog elements like button texts, labels etc., simply by clicking the on the arrows on the right-hand side of the corresponding selection boxes.