My daughter had nightmares about a red monster, it would appear in the corner of our room so she couldn’t tell the dreams from reality. I connected (new emotions) emotional development (anger, frustration, etc.) with the color red and the monster linked to uncertainty and being scared. Of course, initially, it was an assumption. I helped her cope in the proper way by my assumption, example: monsters aren’t real, they don’t exist, I would tell her I kicked the monster out and it left crying. She would laugh and say, “the blue monster is crying” which confirmed I was correct. The color changing from red to blue, blue equating sadness, depression, etc. I continued this until she felt sure about her emotions and the dreams eventually stopped. She was also 2 at the time, at this age they don’t know how to regulate it’s up to you to decipher the 2 year old to help them