To dream of a rat represents underhanded behavior, people, or situations. Rats reflect lying, cheating, stealing, or backstabbing other people.
You may be hiding something from others, or having a problem trusting someone.
To dream of a dead rats may reflect dishonest or deceptive people that have been caught or punished.
To dream of a blue rat represents people or situations that can't trusted that are working hard to earn trust.
To dream of a white rat may represent deceptive or underhanded behavior that is for a good purpose. Lying or cheating for a good cause.
Example: A woman dreamed of a blue rat. In real life her boyfriend had cheated on her and was trying very hard to earn back her trust.
Example 2: Women often dream of seeing their husbands turn into rats when they are unhappy with their marriages. Most likely a reflection of their feelings about their husbands lying or cheating behind their backs.
Example 3: A woman dreamed of rats that scared her. In waking life she was considering telling people about her pregnancy which she had kept to herself, but then had doubts about whether she could trust her friend to keep it a secret.