I have modified in code. try the following:
HTREEITEM hItem;
CBitmap m_Bitmap1, m_Bitmap2, m_Bitmap3, m_Bitmap4;
m_Bitmap1.LoadBitmap(IDB_BITMAP1);
CImageList* m_ImageListTree;
m_ImageListTree = new CImageList;
m_ImageListTree->Create(IDB_BITMAP1, 16, 16, RGB(255, 255, 255));
m_ImageListTree->Add(&m_Bitmap1, RGB(255, 0, 255));
m_treeCtrl.SetImageList(m_ImageListTree, LVSIL_SMALL);