Click the mouse cursor exactly on a Page Number where it appears on a page.
Set the Character Color in the Type panel.
The 'Type' settings are linked to each text field- Photo Text, Page Text, Page Number Text, which allows you to set individual Text Style for each of these three 'areas'.
For Page design and Blurb-
Lightroom includes ~180 page Templates. These are fixed in code.
The existing templates can be modified only by changing cell margins- and then saving the changes as a "Custom Page" (Your changed photo cell margins remain. Text cells remain, but not any typed text!)
There are reports of others re-writing Book page template code, but rare and difficult.
A far easier "work-around" is to create pages in the Print Module and Save (Export) as JPG, for inclusion in a book.
Use [Single Image/Contact Sheet] or [Custom Package], Use a Page Setup for your book page size, then design as much as you want, you have a 'Free Hand'.
(You will need to Import or Synchronize a folder, to get the JPG images into the LR Library.)
The 'saved' JPG image can be inserted into a '1 Photo' full page template.
And- If you save the Print design as a Preset in the Print Module, you can always re-produce the page with other photos!
Random Print Module designs in a Book-
? Index Page-
I have only ever created my Index in MS-Word after I have finished the book layout, then copy/paste it into one of the 'Text Pages' templates. Remember to have a blank page available for the index if you use page numbers, (Inserting or adding a new blank page will change the page numbers!!)
In the Book module you only have some "Creative" page templates, that can be very nice.
I mostly create a "Stroke" Action in Photoshop and apply to my photos for the book, or use the 'Stroke' option in the Print module.
Both the 'Photoshop' and 'Print module' techniques require you to make derivative image files which increases your hard-drive storage consumption. The LR Book module "Creative page" templates do not.
Thank you very much - all really helpful and much appreciated,