light-blue vs pale blue

light-blue and pale blue both are adjectives.

Word	Noun	Adjective	Verb	Adverb
light-blue	No	Yes	No	No
pale blue	No	Yes	No	No

As adjectives, light-blue and pale blue are synonyms defined as:

light-blue (adjective)	pale blue (adjective)
of a light shade of blue	of a light shade of blue