Metal pen cross refills typically come in three common colors: black, red, and blue. Here is a brief description of each:

1. Black: A classic, professional color used for formal writing and note-taking. Black ink is often associated with authority, seriousness, and legibility.
2. Red: A vibrant color often used for corrections, edits, or highlighting important information. It can also be used to emphasize key points in writing.
3. Blue: A popular color for everyday writing, offering a more relaxed and approachable appearance than black. It is often used in offices and schools for general note-taking and communication.