Ombre dyed wool is a dream to work with. Coordinate it with just one or two other colors and your scheme attains a modern sophistication. Combined with Multi, the ombre dyed pieces pull the whole work together in a subtle way. A true favorite.
Spot dyes let you hook several grades of different colors without changing a strand, allowing for a melange effect. Hooking, say, an autumn leaf with a single strip of wool that has been dyed to move gradually from greenish yellow to bright yellow to orange to scarlet gives you a lovely flow and deep color effects.