From Tracker Software PDF SDK
The IsGrayScale method determines if the image page is grayscale. A page is considered grayscale if RGB components are the same within each color value.
HRESULT IsGrayScale([out, retval] VARIANT_BOOL* pGray);
- [out, retval] Specifies the pointer to a VARIANT_BOOL type variable which receives the result.
Returns S_OK if operation was successful or error code in other cases.
IIXC_Page::IsGrayScale may be applied to any image of any type.