Hi @opherv
Welcome to the Auth0!
Thank you for posting your question. Unfortunately, without custom pages, it’s not possible to edit the background or font color of these fields. We already have a feedback page about this issue here: Make it possible to change background color of disabled field on Customization Options for New Universal Login. I encourage you to share your feedback under mentioned post. I will try to bring the team’s attention to this problem, as there are already several user experience problems with these settings.
Thanks
Dawid