Law of Similarity
Things that look alike are seen as related, or as doing the same job.
Why it matters
If a link looks like plain text, or plain text looks like a link, people get it wrong.
How to use it
- Style all links and buttons consistently.
- Do not style non-clickable items like buttons.
- Use differences only where the meaning differs.
Example
If every primary button is blue, a new blue button is understood immediately.