Mark Hendriksen – Buttons
Basic button colour & hover colour set in design tab.
Background of icon section (which is same as button hover colour) & dividing line (which is just a little darker) are set in CSS which is currently sitting in the page settings (but would be put in your Divi Options normally)
Each button has a custom CSS id.
See instructions at: https://www.markhendriksen.com/create-beautiful-divi-button/