Color is often another indicator of trouble. Moles that are different shades can be cancerous. Cancerous lesions can be multiple shades of tan, brown or black. It's also not abnormal to find melanomas that have red or blue coloring to them. 

The diameter of a melanoma is usually larger than a pencil eraser. Sometimes, when detected early, they can be smaller, but it's important to look out for large moles or lesions, which may be cancerous. 

An evolving mole may be a sign of cancer. A mole that changes size, shape, color, elevation or another characteristic, may be a cancerous mole. Additionally, other changes such as bleeding, itching or crusting are also signs of trouble.