When light fades, color go with it, yet this is not just a question of the quantity of light; it's also the quality. Both time of the day and climactic conditions make a big difference. Morning, midday and afternoon light all have a different effect on color, making them cooler or warmer, crisp of vague.
Distance. Color nearest to us appear brighter and warmer than those in the distance; colors seem duller and cooler as the atmosphere in between increases. If you want objects to recede in the distance, they have to lighten, as well.
Surrounding Colors. Every aspect of color is relative. Learn to see each color with a fresh eye every time.