Sure.
Red means stop. No more negotiation, something has crossed a line (too painful, something bad that wasn’t negotiated, etc.)
Yellow means that you need a break or that something is too much, or that if the top continues then you’re going to “red” soon.
Green means that things are going well and you want to continue if not ramp it up a little.
While a bottom might blurt out red or yellow, I’ve never seen a bottom volunteer “green”. It’s usually said in answer to when a top is checking in to make sure everything is okay. Asking “How are you?” and getting an answer of “fine” or “okay” might mean the bottom is just on autopilot and reflexively answering. Asking “What’s your color?” and getting “green” or “I was very close to yellow when you stopped” is much better.
One of my favorite doms to watch at parties was doing a pre-scene negotiation with someone he hadn’t played with before and said something like “Now, just between you and me here 😉 , my favorite color is yellow. It’s not about taking anything I can dish out. I promise you, I can always go harder. I want to know how you’re doing. I’ll likely yellow you, on purpose, a few times, just to find out where your limits are and then aim for a little below that. I don’t want to hear ‘green green green, green green red’ because then the scene’s over. I want some indication of how you’re doing and when you’re getting close to what you can handle, okay?”
And then, whenever she yellowed, he praised her. And why wouldn’t he?? She gave him vital information that allowed the both of them to have more fun!
This is such a fantastic answer and also I’m completely turned on by that kind of negotiation. It makes me feel safe (both as a dominant or a submissive) which helps me relax and enjoy myself. I like giving options when I’m topping. If I’m concerned at all that someone isn’t enjoying themselves or needs a break and is trying to be a tough cookie, I give them an easy out that doesn’t involve much over-thinking. “Should we stop for some water or should I spank you some more?” “Should I fuck you until you cum or does this little pussy need a break?” “Can I take a picture or should I just keep this cuteness all for me?” While I encourage anyone in a D/s relationship to practice speaking up for their needs as much as possible, I also recognize that for people-pleasing personalities in particular it can be helpful when someone puts the “no” on the table first.
Kink negotiation and communication has honestly changed who I am as a person. Everything said above is superb, and I think we should all take a second to marvel at the ways that consent-based culture (and its clear protocols) can help you achieve wildly intense moments of ecstasy and potentially explore previously untapped parts of yourself.