Of course! How do you think evolution happens. Lifeforms don't just grow random arms for no reason. Animals grow different features and abilities because they have a need for that ability.
So it starts as a thought, and over time it will grow.
Of course for humans, because we have a higher level of consciousness, we can make simple changes like height, weight or muscular build easy. Even eye color is pretty simple. I changed my eyes from hazel to a more greenish shade.
Not permanently, because I just quit intending it and thinking about it.
So yes, this is easily possible.