Collar
To dream of a collar represents ownership or belonging. You or someone else that is controlling someone else. It may also reflect how you believe you are someone else's property.
Example: A woman dreamed of seeing a red collar. In waking life she felt she disrespected her husband and felt she should make up for it by proving that she belonged to him.
Example 2: A teenage boy saw a dog wearing a collar that had an envelope attached with a message in it that blamed him. In waking life he lost his virginity with a girl and feared getting her pregnant. The dog collar in this case may have reflected his feelings about the girl belonging to him or his own feelings of belonging to the girl.