Black ink tattoos are excellent on all skin types and colors.
Tattoo ink is deposited and stays in the dermis, the middle layer of skin - under the epidermis and above the subcutaneous layer. The epidermis (top layer) is where the melanin lives in your skin. This is what pigments your skin tone. Since your natural pigments are in the layer above where the ink stays, you must imagine viewing the ink's color through your natural color. When you get a fresh tattoo the ink is dispersed throughout the epidermis as well so it may seem brighter right away, but this usually heals over during the first month. Generally, you will always get great healed results with an ink color that is darker than your natural skin pigment.
The only recommendation I would make regarding my work on someone with a darker skin tone would be to utilize areas of high contrast either with bolder lines or areas of solid black. Finer lines still look great on any skin tone, but having some high contrast areas can help the design continue to read well as it ages.
Here are a few examples of how my work looks on various skin tones!