Final answer:
The most fitting word to complete the statement 'COLOR youth: ___' is 'enthusiastic', as it captures the spirit and energy often associated with both: vibrant colors and youth.
Step-by-step explanation:
The missing word in the given statement 'COLOR youth: ___' is somewhat subjective and could technically be any of the four options provided, as they all can describe characteristics that might be associated with youth. However, if the context is considering youth as being full of life and spirit, option 4) enthusiastic could be the most fitting choice. It is worth noting that the word color in the initial part of the statement does not necessarily indicate that we should pick a word related to colors directly, but rather a characteristic associated with the vibrancy often implied by colorful imagery.