Why are SumoSprings different colors? The different SumoSprings’ colors identify their density. SumoSprings come in three different densities: blue SumoSprings are -40, black SumoSprings are -47, and yellow SumoSprings are -54. Blue – 40 Blue -40 density captures more air in the millions of micro-cellular bubbles, creating an air spring suitable for light and medium duty applications. Black – 47 …