Modifying color and hover color of search button

Hello to you all, I would like to change the color & hover color of the search button located in the menu at the right side. The native color is green. There doesn't seem to be an option to modify this (yet) under theme options: "Header Right Menu Color Options" or "mobile menu". Also, when you click on the search button, there appears a white 'search'window with on top a green line. That green line I would like to change into blue as well. Could you help me in order to do these modifications please? Thanks already in advance for your help. Best regards, Bram