As a new employee who would, one day, like to be an old employee, you may try considering the employers perspective.
Your boss, whether called the owner, director, supervisor, foreman or just plain Sir, is probably indifferent to your keyboard preferences. Bosses tend to care about your ability and willingness to do the task you were hired to do. They aren't looking for characters or individuals. They hired you to do a task that needed to be done. Period.
With that in mind, ask to use your personal keyboard, not because it makes you smile, not because you like the sound it makes, not even because it's more comfortable to use. Ask to use it because it allows you to work better and faster.
As others have said, it's best to leave the board at home that has the rainbow caps, the noisiest click and the flashing lights that spell out "I'M SPECIAL".
Just a nondescript keyboard.