Direct psychoanalysis:
If the external factors of daily events are uncertain, the dreamer must always suppress his reaction. This is impossible in dreams, so the dreamer's mind looks for another way to solve the problem. He dreamed that the color of the monster (see color) can often hint at some problems. The red monster represents anger (perhaps uncontrollable anger), and the yellow monster represents jealousy and envy.
Subconscious spiritual symbol:
On the spiritual level, the monster in the dream symbolizes the fear of death and everything related to death. Monsters can also show more pure fear.
There must be some emotions hidden in your heart that you can't vent. Nothing, just a dream. Don't worry.