Here's one method:
While glowing text takes up unnecessary CPU you could install the hack then edit out the custom_profile_field1 (or whatever number you set it at) in the public_register_form.pl, public_reg_confirm.pl, public_reg_confirm_kid.pl and public_edit_profile.pl files. This is to prevent users from adding the font colors. Then as an admin you can do it via CP for the users you want. If you want selected users to choose their font colors and not you then I guess you will have to code a checkbox as they do with forum access.
