Only Global Admins can make this change. From the Home Page of the Adminstration Dashboard> Click the "Administration" section. > then Click the "Site Settings" icon. Under the General Settings header you will see a question field called "Applicant Side Theme" click the "Click Here" button to the right of that field. This will open up a new screen where you can edit the theme colors. You can enter your Pantone Color or choose from a color wheel.
NOTE: The text that shows on this screen is not your data it is just sample data to give you an example of what the theme will look like.