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, resulting in broad rolling spectra for LCDs.

The difference in the relative heights of the Green and Red Primary peaks for the Tablets is due to their different White Points, which requires different drive levels for each primary.

Note the very sharp and highly saturated colors for the Kindle Fire HDX 7, which are quite similar to the spectra of OLEDs.