adverb, adverb taking the 'to' particle, noun or participle which takes 'suru'
vividly green; lush green; verdant; deep blue
Describes lush, fresh greenery or a vivid blue sky/sea. Often used adverbially with と or as a する-verb to mean 'be verdant' or 'be deep blue'. The 'deep blue' sense is less common and typically poetic.
田んぼが青々としている。
The rice paddies are lush and green.
空が青々
The sky cleared up to a deep blue.