Need assistance changing the default theme

The login and register buttons have the background and text colors that we want to use.

Once logged in, the logout button and My Account dropdown colors change and are hard to read. In addtion, the Account dropdown items aren't visible until you hover over them.

I need to make the logout button look the same as the login button and the Account dropdown and dropdown items to have the same color as the Register button.

Can someone help me to make these adjustments?

thank you!