You can use a style sheet class to make buttons look different from their current appearance.
The Button Style Class
input provides a hook to apply any CSS-related styling on buttons. You can use various methods to include a style sheet. For example, you can add a Style Sheet builder, use a portal theme, use the base HTML page, or a page automation template.
Simply set the Button Style Class
input value to the name of the class to be used for the popup Calendar Button.
Parent topic: Calendar Picker builder