I just did some google work on what color ribbons and what they mean...
RED- Horse kicks and should be given pleanty of room.
GREEN- Horse is either green broke, not use to the type of riding being done, unpredictable or uncontrolable in anyway, or if they are not use to being ridden in a group and you are out with a group.
YELLOW/WHITE- This horse is a stallion.
Mares in heat who get testy and foul tempered may also wear a ribbon. The color of this ribbon is not important so long as it may be seen. Red is commonly used since mares in heat are known to be more likely to kick. Blue is also a good color for foul tempered mares.
So there are the ribbons lol hope this helped everyone. I have to go buy a red ribbon sometime soon....Bause has been proven as a possible kicker...lol