I wouldn't do anything more than change them from #333333 to #333... why?
1) you might change your mind and want them different colours.
2) because the colours are assigned to different attributes on different elements, anything you do to it is going to be more code.
See nonsense like HTML/CSS "frameworks" that make you use two to ten times the HTML needed to do the job; or CSS pre-processors (LESS/SASS/SCSS) that result in writing as much if not more code than you'd have without it that then results in twice the CSS on deployment! Yet then the fanboys make wild unfounded claims these train wrecks of how not to use HTML or CSS make the process easier, or simpler, or "aids in collaboration" or some other made up fairy tale not based in anything remotely resembling reality.
No matter what anyone tells you more code is rarely simpler or easier. Two to ten times the code? Forget it.
Bottom line, that's as simple as it gets. You want to change them en-masse search/replace in your editor is your friend.