Techwiki:Win32k/PALETTE

typedef enum
{
    PAL_INDEXED    = 0x000001,
    PAL_BITFIELDS  = 0x000002,
    PAL_RGB        = 0x000004,
    PAL_BGR        = 0x000008,
    PAL_CMYK       = 0x000010,
    PAL_DC         = 0x000100,
    PAL_FIXED      = 0x000200,
    PAL_FREE       = 0x000400,
    PAL_MONOCHROME = 0x002000,
    PAL_DIBSECTION = 0x008000,
    PAL_HT         = 0x100000,
    PAL_RGB16_555  = 0x200000,
    PAL_RGB16_565  = 0x400000,
} PAL_FLAGS;

The EPALOBJ struct is of variable size.

typedef struct _EPALOBJ
{
    BASEOBJECT      BaseObject;    // 0x00

    FLONG           flPal;         // 0x10
    ULONG           cEntries;      // 0x14
    ULONG           ulUnique;      // 0x18, looks like a counter more than a time, like Yuan suggests
    HDC             hdcHead;       // 0x1c
    HDEVPPAL        hSelected;     // 0x20, same as hdcHead::ppdev
    ULONG           cRefhpal;      // 0x24
    ULONG           cRefRegular;   // 0x28
    PTRANSLATE      ptransFore;    // 0x2c
    PTRANSLATE      ptransCurrent; // 0x30
    PTRANSLATE      ptransOld;     // 0x34
    ULONG           unk_038;       // 0x38
    PFN             pGetNearest;   // 0x3c, points to win32k!ulIndexedGetNearestFromPalentry
    PFN             pGetMatch;     // 0x40, points to win32k!ulIndexedGetMatchFromPalentry
    ULONG           ulRGBTime;     // 0x44
    PRGB555XL       pRGBXlate;     // 0x48
    PALETTEENTRY    *pFirstColor;  // 0x4c, this->apalColors, attention!! Yuan is wrong here
    struct _EPALOBJ *pPalette;     // 0x50, this, attention!! Yuan is wrong here
    PALETTEENTRY    apalColors[1]; // 0x54
} EPALOBJ, *PEPALOBJ;