Possible Clues:

• Dull-coloured flag, say, never raised
• Colour when wise person suggests they're naive
• French painter losing head about place for putting colour
• Decline to follow sun, wanting experience of shade
• Lawn shade
• Avocado relative
• Colour of plant showing contrasting levels of maturity
• A shade more sensible than the others?
• Shade for the wise environmentalist
• Dull colour for the prudent environmentalist