Select File > Settings and then choose Appearance in the left list.
Font family — Font for text displayed in the interface.
Fixed-width font family — Font for displaying code in the interface.
Font size — The font size for text displayed in Pirana.
Additional note colors — Code for colors, other than default colors, to use for marking/filtering models. The colors are listed when 
is selected in the main toolbar.
To find a color code, go to https://www.rapidtables.com/convert/color/rgb-to-hex.html and use the sliders to select a color. Press Convert to display the 6-digit hex code (e.g., #9425EF, which is deep purple). Then enter the code (omitting the #), e.g., 9425EF, into the field, and the color will appear as an additional option in the list.
Windows-style button order — When checked, places the Cancel button on the far right in dialogs (as shown in the images within this document). Unchecked places the Cancel button on the far left (unless the dialog has a Help button, in which case the Cancel button will be the second button from the left).
Position standard dialogs over main window — When checked, centers common dialogs, such as file or folder selection dialogs, with respect to Pirana’s main window.
If unchecked, the dialogs are positioned in the top left corner initially. Note that, if the common dialog is moved, the new position is remembered.
Center standard dialogs to their parent window — Works the same as the Position standard dialogs... option, except that the common dialogs are centered with respect to the window from which the common dialog was called (i.e., the parent window).
Theme to use for the editor — Color theme for the built-in editor.
Font size for editor — Font size for text displayed in the editor.