How to let a .myhtml file has colors as a html file in vim?

I have a html file, it has good colors in vim.

But I want to define some custom file types, they have html content, 开发者_如何学Pythonbut with different suffix names. e.g. index.html -> index.myhtml

But when I open "index.myhtml", it has no colors, only black and white.

How to let the vim treat the ".myhtml" as ".html"?

Thanks in advance!

1. :set filetype=html

2. write in .vimrc

   au BufNewFile,BufRead *.myhtml set filetype=html