Plugin Input box / cookie question

[Mike]

I have been looking at a few plugins with configuration options, and I
am hoping to better understand what they are doing . . . (in example)
http://www.tiddlytools.com/#SearchOptionsPlugin
http://visualtw.ouvaton.org/VisualTW.html

It seems like in the beginning they are defining a cookie, and giving
a text / input box so the user can define the cookies value (sorry if
my terminology is wrong / terrible) and then the plugin can later use
that value / cookie.

So I just made my first plugin/macro today (with some help of course)
and I was wondering if I could use this method or something similar to
make the (5) colors I defined in .setStylesheet user definable without
having to edit.

While the obvious solution is to just change the plugin code or create
a override in the stylesheet - I am more hoping to better understand
what is going on, and learn something new.

Thank you for your patience and time ! (regretfully I am more of an
enthusiast than a programmer)

Mike