One thing you and your colleague both have in common is your workspace. If you’ve noticed their desk looking a little drab lately, why not buy them a cute gift to help brighten the place up? This could be a pretty ornament, or maybe a novelty item that you know will make them laugh. If you want to get a more practical gift, opt for a colorful desk tidy or some new stationary. It might sound dull, but your colleague will be touched that you made the effort to help them out!
Take them out for a meal…
…or any other kind of activity. Being friends at work is fine, but if you both get on, why not make some time for each other outside of work too? It can often be nice to relax outside of the work environment, not worrying about whether your boss has caught you chatting for the third time today. Take your work friend out for food, or suggest that you catch a movie together – all on you, of course. You may find it refreshing to socialize outside of work, and who knows? It could become a regular thing.