After requests from several folks for a communication preference system, we'll be implementing a system this year for folks who sometimes find interaction with other people overwhelming.
Yellow and red clips will be available at the registration desk and the info desk. You can collect these at any time you like and keep them until you need them. When you need to use them, just clip them to your lanyard, somewhere clearly visible to other people. (This system is based on systems used at Autistic spaces and conferences.)
The clips can be used to indicate the following:
Yellow: "I only want to talk to people I know right now. If we've met before, it's okay to talk to me."
Red: "I'd prefer not to talk with anyone right now. If I start a conversation with you, it's okay to talk to me."
Please respect other attendees' communication preferences and do not talk to them if they are wearing a clip which indicates that they do not want to be disturbed. If you have any queries about this system, please contact email@example.com, or @9Waccess on Twitter. Thanks!
Lastly, it's okay if you make a genuine mistake because you didn't know - like if you didn't see someone's badge or clip, or forgot what it meant. Don't beat yourself up about it! Just keep an eye out for next time.
Edited To Add:
Following popular request, we're adding a third option!
Blue: "I would like to talk to new people but find it difficult to initiate conversation. Please say hello!"