Assign the appropriate mood to this excerpt.
The sky was a deep pink as the sun set on the horizon.
The mood of this excerpt is serene and tranquil.
Complete the following task based on the instruction and optional input provided.### Instruction:
Assign the appropriate mood to this excerpt.

### Input:
The sky was a deep pink as the sun set on the horizon.

### Output:
The mood of this excerpt is serene and tranquil.