One thing to keep in mind with the Tung oil is that it is not so suitable for wet weather - it can develop black mold.
There is quite a long faq on what to paint your hive with here:
Many beekeepers use oils such as Tung oil or Linseed oil, however we have found when finishing with oils in wet climates, that mildew (black mould) can grow on the surface of your hive. While this will not affect the structural integrity of your hive and should not have any impact on your bees, this may not be the look you were anticipating.
It can be a challenge keeping wood outdoors looking like new, especially in wetter climates. If you wish for your hive to stay mould free and to maintain the natural timber look for as long as possible, we suggest you go to your local paint store and ask for a finish that will last outdoors.
When choosing a finish you will be faced with the choice of natural or non natural finishes. If you go with a less natural finish we recommend you leave the inside of the timber boxes unfinished to keep the internal wood natural for the bees. However, it is advisable to coat the inside of the window covers to stop these from expanding excessively in wet weather. If the finish has a strong smell it is recommended to leave it a few days before installing your bees.
Aside from mildew, wood outdoors will naturally turn to grey. If you want to prevent your hive from greying, paint stores will recommend a finish with a tint. The tint helps shield the wood from UV which is what turns the wood to grey.
If you want to paint your hive with an outdoor paint, this is a great option for protecting your hive from the weather. This will also give you the opportunity to get creative with your designs.
Some commercial beekeepers recommend dipping your hive boxes in copper Naphthalate, then painting inside and out with several coats. While this has proven to make bee boxes last a long time, we like to recommend you use a more natural finish.