Why NERDTree do not highlight

Hi,

 

The following features and functionality are provided by the NERD tree:

* Different highlighting is provided for the following types of nodes:

        * files

        * directories

        * sym-links

        * windows .lnk files

        * read-only files

        * executable files

 

         In my _vimrc ,

         let NERDChristmasTree=1  

        

         it is not highlight!

 

Best

         Regard