It transitions from color to color. Instead of just changing from one color, it goes through all the colors in between the two colors.
RGB light does this. RED-GREEN-BLUE-RED-GREEN-BLUE and so on.
this light fades. Red-orange-yellow-green-blue-purple-red....And it's not just a flash to the next color. It fades.
To be honest, I see no relation between the two lights other than the fact that they both change colors. They don't change the same way, and they don't only have the same three colors.