Thanks for the response.
Unfortunately, I couldn’t notice any difference in the menu height after including your code in the custom CSS. The code is still included if you could take another look, please.
Also, with regards to changing the color, perhaps I was not very clear. I would like to have a different colours for second tier menu items and top tier menu items. The setting in theme options ->styling ->menu only controls the colour for the whole menu, but I’d like to have different colours on different tiers.