With vim >= 8 you can use the package mechanism directly included inside vim.

mkdir -p ~/.vim/pack/user/start
cd ~/.vim/pack/user/start
git clone https://github.com/alkino/vim-mod-syntax

It will now directly work when you open a file ending with .mod.

If the file does not end with .mod, once the file is open type

:set filetype=Mod

Works directly with:

call plug#begin()
Plug 'alkino/vim-mod-syntax'
call plug#end()

Here, is an example of coloring