Most of them will not change.
And my thought is, if you want to ride a horse and buggy, you can't expect to have air-conditioning and a cd player. I know this is frustrating, but at some point I gave up trying to make things work for people using ancient browsers. If they won't upgrade, so be it.
I'm have used the Graphene options panel to create menu gradients.
If you use those options, they will override the default css. You'll need to clear those options in order to see the default css be displayed. (The "C" in "CSS" means cascading, so whatever get applied last is what you see. The Graphene color options is what you see last if you use your browser's "View Source" option.)
I want so see the CSS that controls menus. I can't find it anywhere.
Take a look at the default Graphene style sheet. It is well-commented, so you should be able to find what you are looking for. (A caveat: menus can be complicated.)
Have you tried clearing the browser cache? And have you tried installing Firebug, which is what every web developer needs. Using Firebug will answer just about every question you've asked here. Josh has a good tutorial here: