First and foremost no one can copyright an idea. If copyrighting ideas was permitted then the entire world would be in some serious trouble. Anyways
Candy Crush Saga is just another match 3+ game that happens to utilize little candies
Second, the themes can be used in any way as long as the game somehow uses the theme in some way (conventional or non-conventional). Take for example the first SFML Game Jam with the theme of "Lights and Shadows!".
The games that were produced used this concept in so many different and unique ways. Now considering how the theme you are talking about and how generic it is, just sitting here I can think of multiple ways to integrate this into a game design.
And third, the themes are suggested by the community and voted on by the community.
So the community will decide if it is a good theme. The only reason I would remove themes is if they contain inappropriate language.