The phrase "castle sky" typically refers to a deep blue or violet hue, often seen at sunrise or sunset. Synonyms for this term include "purple sky," "lavender sky," "indigo sky," and "royal blue sky." Other phrases that describe this color range might include "dusk sky" or "twilight sky." These colors can also be used to describe the evening sky as it transitions from day to night. No matter what words are used to describe it, the sight of a castle sky can be mesmerizing and awe-inspiring, evoking feelings of tranquility and wonder.