After your edit, it's clearer to understand what you need. In that case, I do not think a Sequence Diagram is the best choice. The sequence diagram models the communications (or transitions, if any) over time between the entities involved. Thus, its great use is to represent the logical sequence in which actions, usually in a specific use case, are carried out by all involved (users and components of a system).
From what I understand, your interest is more in the sense of representing two things:
The logical structure of the website, ie which pages are linked to which other pages
Properties of certain transitions, such as if only one profile is able to make / allow certain transition.
So, I agree more with colleague's answer @rray about using State diagram . In it you can represent each page as a state of your system, and in the transitions add information (even the color you suggested yourself) to indicate its properties.
Wireframes, which I I mentioned in comments , would be most useful if you want to go into a higher (but not final - that is, very low level) detail level as to which areas of each page should allow transitions. This helps you not only plan transitions but also other aspects of user interaction. In this more informal type of diagram, you can draw the transition arrows from specific areas of a screen sketch, for example to indicate whether the user should always click on the same region to navigate, on side columns to access tools , etc.
It should be noted that although I think the Sequence Diagram is not the most appropriate, it does not mean that you can not use it. You will probably only have to do several of them, for each scenario navigation. And even though I am answering this question with the best that I can infer from my experience, I still think it is a bit opinion-based, as there is no truly correct answer.
