CSS Change style of the login button

Hi,

Im having some overlap issues with the upfront login feature, it seems sometimes the overlap allows page content to go above it and when scroll down it looks fine. see screenscast - https://monosnap.com/file/fRuPTZEDweXeaUc8SE7wEvhbJDZIaM

also is it possible to change the text colour or the login link to White and then When hover/ selected yellow (same as the menu items on the left of it) ?

Support Access is open
domain - http://tinyurl.com/plletgb

Thanks

Tom