Palette concept in LCD controller of LPC2478

Hi,

 I'm successful in interfacing TFT lcd with lpc2478. TFT lcd is 24 bpp
depth.
Image which i want to display is captures too much memory, So I want to
change depth to 8 bit for TFT display. I have not clear idea about
"palette" in LCD controller. I gone through nxp site but there is no any
application/technical note about this.
 does any one have idea about how to use palette in lpc2478, any
information about the working of lcd ,means why & how to use palette.
 if any link about this or article would be better for me.

Thanks in advance
J.