They didn't do it your way. This is what they added to windows.h:
Code:

---

 
typedef DWORD COLORREF;
typedef struct CHOOSECOLOR {
    long lStructSize;
    long hwndOwner;
    long hInstance;
    COLORREF rgbResult;
    COLORREF *lpCustColors;
    long Flags;
    long lCustData;
    long lpfnHook;
    char* lpTemplateName;
} CHOOSECOLOR;

#define RGB(r,g,b) ((COLORREF)(((BYTE)(r)|((WORD)((BYTE)(g))<<8))|(((DWORD)(BYTE)(b))<<16)))
#define GetRValue(rgb)      ((BYTE)(rgb))
#define GetGValue(rgb)      ((BYTE)(((WORD)(rgb)) >> 8))
#define GetBValue(rgb)      ((BYTE)((rgb)>>16))

BOOL WINAPI ChooseColor(CHOOSECOLOR* lpcc);
#define PRAGMA_API ChooseColor;comdlg32.dll!ChooseColorA
 

---

I figured out my problem: lpCustColors cannot be null