From the WDWCP website:
"Sunglasses are a block to interpersonal communication with guests and should be avoided if possible. As a general rule, they may be worn in jobs where glare from water, counter tops, direct sunlight, etc., would prevent you from doing your job safely or efficiently. Only sunglasses that allow your eyes to be seen are permitted. No mirrored or dark, opaque lenses are allowed. Sunglasses are not to be worn at night, in dark areas, or indoors. They should be removed when engaging in extended interactions with a guest. Sunglasses should not be visible when not in use.
The frames and lenses of both eyeglasses and sunglasses should be a neutral color, such as black, brown, or metal rimmed (for frames), with a conservative style and no contrasting logos. Frames and lenses in shades such as blue, green, pink, yellow, etc. will not be permitted, as they are not neutral colors. Glasses and sunglasses should not detract from the costume or contradict the theme of the show. Prescription eyewear must also meet these guidelines.
The use of leashes or cords with glasses or sunglasses is permitted on an exception basis only, for Cast in certain limited roles. If a specific department or area requires the use of leashes or cords for safety reasons, please contact the Cast Image and Appearance Office for approval.
If colored or tinted contact lenses are worn, the resulting eye color must be natural looking and appropriate to your skin tone. Decorated lenses are not permitted, nor are any looks which would be considered distracting or not in the best interest of our Disney show. "