Favorites can be set for a Sim in Create a Sim as part of their personality in The Sims 3. There are three types of favorites: food, music, and color. Sims will tend to choose their favorites when they can.
In The Sims 3, Sims have a favorite color. It doesn't exactly have any purposes for Sims. In The Sims 3: Into the Future, using the sonic shower with the Sim's favorite color will increase their hygiene in no time as well as grant the "Favored Cleansing" moodlet. Drinking the favorite color of a drink from the drink synthesizer will give "Favored Drink" moodlet, while drinking the opposite of their favorite color will give the "It is Revolting" moodlet instead. The favorite color and its opposite for the drink synthesizer are set against each other in the list below.
The purpose of the favorite food is apparent: Sims who eat their favorite food will clap and laugh as they eat, and might get a moodlet and a mood boost. Sims will choose their favorite leftovers more if told to eat. With Late Night or Supernatural, vampires will prefer O-positive plasma, a type of blood in real life.
Showtime or patch 31 included some new vegetarian and tofu-contained recipes. These recipes are the alternatives of the existing recipes.
There are favorite food icons for hot wings, nachos, olive platters, onion rings, shrimp cocktail, and hot and sour soup in the game files, but they are actually not favorites in the game.
Sims listening to their favorite genre of music will get a mood boost. If the player chooses the "Dance" option, the sims will turn it to their favorite radio station.
Due to a glitch in the game, it was possible to have a Sim's favorite music be "French" without The Sims 3: World Adventures. This was fixed in game update 1.8/2.3 on 12/15/09. Subsequent expansion or stuff packs will also change a Sim's favorite music from "Custom" to anything else.