To dream that you have a suntan, signifies the shadow aspect of yourself. It represents your primal instincts and natural senses. It is also indicative of hard work and owning up to your responsibilities.
To dream that someone else has a suntan, suggests that you not acknowledging a quality or aspect of that person within your own self.
Being suntanned, as in having darker skin as a result of sun exposure, could represent:
Protection from or adapting to the environment
Time spent outdoors
Vanity, superficiality, or insecurity about what others think
An attempt to compensate for low self-esteem