New to Square and just sent myself a test invoice by email. The email banner/header picked up my brand colour as per my settings, however the "pay invoice" button is blue (see screenshot I don't have permission to upload images here?). I presume this is Square's blue colour. When I click through, the "pay invoice" button is my brand colour, so this is good. Can the email template be updated to pull the brand colour through to the pay invoice button?
