The Backlights for LCD displays are white LEDs, which are made by using a Blue LED together with a yellow phosphor to transform some of the light for the Red and Green primaries. The spectrum of an LCD display is just the spectrum of its white LED Backlight filtered through the individual Red, Green and Blue sub-pixel filters within the LCD panel.
The LCD RGB spectra are a broader filtered broadband spectrum from the White LEDs, which results in less saturated colors. When more saturated colors are desired, the LCD light output decreases, which then requires more power for the Backlight LEDs.
The iPad 3 has a more extreme Red and deeper notches between the primaries, which gives it greater Color Saturation than the Surface RT, iPad 2, and Galaxy Tab 10.1. The varying heights of the Green and Red Primaries between those Tablets is the result of their differing White Points. The Surface RT has the warmest White and the Galaxy Tab has the bluest White.