Which statement correctly compares regulatory, warning, and guide signs under MUTCD-style classification?

1. Regulatory signs are always yellow, warning signs are always green, and guide signs are always red
2. Regulatory signs state laws, warning signs alert to conditions, and guide signs provide route or destination information
3. Regulatory signs are optional, warning signs are enforceable speed limits, and guide signs prohibit turns
4. All three classes mean the same thing if they are rectangular