What does consent mean to you? Most of us think of consent as a “Yes” or a “No” when it comes to sex. But really, whether in a vanilla or kinky relationship, there’s more to consent than that. Plus, some D/s relationships play with consensual non-consent. Some relationships have a rule that as long as the submissive is with the Dominant, consent is implied.
See? Much more than a yes or no question. Think about consent and what it means to you.
With so many rape cases in the news, especially in college, I'm of the strong belief that consent requires a consistent, enthusiastic agreement to continue whatever activity is occurring. I think the light system is a good way to show that. "Green" is definitely consent to continue, and "yellow" is permission to continue, but maybe slower or differently. "Red" or another safeword is the revocation of consent and the scene stops immediately.
Obviously, if there's a ball-gag involved or the submissive is a little too far gone to speak, or consensual non-consent is at play, that normal version of consent is a little hard—if not impossible—to give. In those cases, I would say maybe safe gestures or signals would be a good way to revoke consent, but that doesn't really leave space for a "slow down" signal like "yellow" unless there are 3 signals correlating to the light system.