I have been adding some custom CSS to the Basic Template application to try and bring the design more in line with our organisation's branding. I have been mostly successful, but am having trouble changing anything relating to the search button.
Currently it still has a grey colour by default, which changes to white on hover. I want to change those colours. I managed to make changes to the colour and hover colour for the search input bar, but this has stumped me. What class or id should I be looking for?

Any suggestions would be great.