Final answer:
Addison's disease causes hyperpigmentation, leading to a deep bronze color of the skin, which is due to the excess production of ACTH.
Step-by-step explanation:
Addison's disease is characterized by the hyposecretion of cortisol from the adrenal cortex. It often results in hyperpigmentation, giving the skin a deep bronze color. This occurs because the disease prompts the production of excess adrenocorticotropic hormone (ACTH), which stimulates melanin production, leading to a darker skin tone. Other diseases can cause different changes in skin color, such as liver disease causing jaundice (a yellowing of the skin) and certain conditions that can lead to cyanosis, where a blue color is observed due to lack of oxygen. However, for Addison's disease, the distinctive sign is the bronzing of the skin and this can often be treated with replacement hormones.