In Visual C++ App, disabled toolbar buttons show as solid grey boxes

I have a VC++ app created using VS2012.  In said app, I have a few toolbars.  When the toolbar images are enabled, the images on each toolbar button display nicely.  However, when a toolbar button is disabled (intentionally), the image(s) on the toolbar buttons display as a solid grey boxes, instead of as a greyed out (disabled) version of the original image.

Here's some more detail:

I am loading the images at run-time by using the following:

CToolBarCtrl& bar = m_wndMyToolBar.GetToolBarCtrl();      
CImageList *pList = bar.GetImageList();      

HICON hIconSomeImage = LoadIcon(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDI_SOME_ENABLED_ICON));      
      
pList->Replace(0, hIconSomeImage);       
      
bar.SetImageList(pList);
m_wndMyToolBar.Invalidate();

This code works well to get the image to display when the toolbar button is enabled.

To solve the issue of the image being a solid grey box when the toolbar button is disabled, I tried creating an image list for disabled toolbar images, as follows:

CImageList m_imgListDisabled;
imgListDisabled.Create(16, 15, ILC_COLOR32, 8, 8);

HICON hIconTest = LoadIcon(AfxGetInstanceHandle(), MAKEINTRESOURCE(IDR_SOME_DISABLED_ICON));
      
m_imgListDisabled.Add(hIconTest);      
bar.SetDisabledImageList(&m_imgListDisabled);
m_wndMyToolBar.Invalidate();

The above code compiles, and runs without throwing any errors, yet the net result is a solid grey box instead of the disabled image.

I should add that the images I am using for the toolbar buttons are icon files (.ico files), and these icons have a high color depth.

Any help would be greatly appreciated.