Based on the clue 'a letter added to spout causes it to do this begin...', what is the answer?

What is referred to by 'a less vibrant hue'? Based on the clue 'a lesser official in a royal household some are of...', what is the answer? Based on the clue 'a lesson on sharing the rainbow', what is the answer? Based on the clue 'a letter added to amiable gets you this word that ...', what is the answer? Based on the clue 'a letter c in orange with white trim', what is the answer? Based on the clue 'a letter expressing thanks for hospitality is name...', what is the answer? Based on the clue 'a letter from einstein to fdr is on display at the...', what is the answer? Based on the clue 'a letter like p or d where some part of the mouth ...', what is the answer?