As experts say, DeltaE (dE) represents a measurement between the color requested and the one really displayed on the monitor. The higher the result obtained, the less true colors are.
More precisely, here is how to interpret the graphs:
Delta E > 3: the desired color is noticeably different from the one on the screen.
2 < Delta E < 3: color quality is satisfactory, but a graphic designer probably wouldn’t be content.
1 < Delta E < 2: colors are accurate.
Delta E < 1: the result is perfect.

Color accuracy is measured with Gretag colorimeter paired with Eye-One Match 3 and LaCie Blue Eye Pro calibration software to double-check the results.