Require vim-syntax-extra
git clone https://github.com/Manu-sh/NeonVimColorscheme
cd NeonVimColorscheme
# now copy the colorscheme in your vim own runtime directory usually (~/.vim)
VIMRUNTIME=$HOME/.vim
# create the colors directory if doesn't exist
mkdir -p $VIMRUNTIME/colors
cp neon.vim $VIMRUNTIME/colors
Then edit your vimrc and add/edit this line
colorscheme neon
or open vim and type
:colorscheme neon