Use IconContext as mentioned in the Docs.
function BlueLargeIcon() {
return (
<IconContext.Provider
value={{ color: 'blue', size: '50px' }}
>
<div>
<FaBeer />
</div>
</IconContext.Provider>
);
}

To target specific Icon Components, you can use the style prop or use the same API (see Configurations) on the component itself:
const style = { color: "white", fontSize: "1.5em" }
<FaFacebookF style={style} />
// API
<FaFacebookF color="white" fontSize="1.5em" />