Appears that PALETTED has been removed from the FTx Developer guide.
Forum thread here
There is a difference between ft80x and ft81x:
"PALETTED8 format is supported indirectly in FT81X and it is different from PALETTED
format in FT80X. To render Alpha, Red, Green and Blue channels, multi-pass drawing action is
required."
#define ARGB1555 0 #define L1 1 #define L4 2 #define L8 3 #define RGB332 4 #define ARGB2 5 #define ARGB4 6 #define RGB565 7 #define PALETTED 8 #define TEXT8X8 9 #define TEXTVGA 10 #define BARGRAPH 11 #define PALETTED565 14 #define PALETTED4444 15 #define PALETTED8 16 #define L2 17

Appears that PALETTED has been removed from the FTx Developer guide.
Forum thread here
There is a difference between ft80x and ft81x:
"PALETTED8 format is supported indirectly in FT81X and it is different from PALETTED
format in FT80X. To render Alpha, Red, Green and Blue channels, multi-pass drawing action is
required."
#define ARGB1555 0 #define L1 1 #define L4 2 #define L8 3 #define RGB332 4 #define ARGB2 5 #define ARGB4 6 #define RGB565 7 #define PALETTED 8 #define TEXT8X8 9 #define TEXTVGA 10 #define BARGRAPH 11 #define PALETTED565 14 #define PALETTED4444 15 #define PALETTED8 16 #define L2 17