Yes it can be shiny and will be different to the normal Ho-oh.
'One of the legendary boss Pokémon, Ho-Oh, can be battled as a Shiny. When Shiny, it has more HP, different moves, and is more powerful in general'
Source: Bulbapedia under the Trivia section
Edit: I changed 'Serebii' to 'Bulbapedia' as I am stupid!