You can use the custom page, text and edition attributes with any GNML tag prefixing the attribute with '@'.
Example
You created a custom attribute in the page object, the attribute name is colorVar and it specifies a custom color
Use it in this way:
>co !@pg_colorVar!<
The prefix pg_ is mandatory for the custom page attributes, the prefix tx_ is for the custom text attributes, while it is ed_ for the custom edition attributes.
Why some attributes doesn't appear on page/in text?
After creating a new article where you want to insert a tag or style with the section-level color, save the page in order for the color to appear correctly in the text. Also, save the page after pasting article frames that contain the section-level color onto page in another section. This requirement is due to the fact that the section-color attribute reads a value from the database, and the database gets updated when you save a page.
Moreover, if the alerts are not enabled in your preferences, you will need to refresh the page manually after pasting article frames that contain the section-level color onto page in another section. See Enable receiving of automatic alerts in Ted4 or Fred4.
See also
Add edition/page/text attributes and access them in tags