Try RMail PRE-Crime Services – The Branding tab is available only to customer admins. In it, company administrators can customize the color theme of the new signer's interface. The configured colors are applied at a global level, meaning that once the theme is changed, it will affect all envelopes sent after the signer's interface colors have been updated.
Note: By default, this feature is disabled. Contact your customer support representative to have it enabled.
Read more about the settings page in general here.
This article describes every setting found in the Branding tab:
Color theme
Company administrators can select one of the three predefined themes or create a custom theme.
Once the color theme is selected, you must choose the color for the header, subheader, Finish button, and Apply button.
In the image, you can see how the selected color theme is reflected in the signing interface