Penalty cards are used by sports referees to warn or penalise players. The yellow card means a warning, the red card means a penalty (often ejection or disqualification). These symbols are often used in a figurative sense.

Some emoticon sets include both cards:

• Club Penguin emoticons list #418
• MaxQDA emoticode list #419
• Emoji.com Sport list #316 (also includes the “second yellow card” (showing both cards at the same time, which is specific to soccer), “soccer referee with red card” and “referee variation with yellow card”)

Standard References

• Unicode Technical Standard 51 “Unicode Emoji” (beta)
• How to propose emojis to Unicode
• How to propose other additions or changes to Unicode (required form, email address: docsubmit＠unicode.org)
• Unicode document submission form