Hi Ying,
Thank you. I should have tested this on different browsers. The main menu now looks totally mad on Chrome and still has the same issue in Safari (Home icon missing on front-page).
What we wanted to achieve was plain white with always the same font color #004e9b. But obviously there is more to it and I have to figure out which changes in the past might have messed this up.
I would appreciate a quick look that might point me in the right direction.