In your terminal Vim session, type :echo g:colors_name to find out if you have a colour scheme set. Also what version of Vim are you using? If you are using V

In your terminal Vim session, type :echo g:colors_name to find out if you have a colour scheme set. Also what version of Vim are you using? If you are using Vim-Tiny for example, it is not compiled with syntax highlighting support. Type :version to see the list of compiled features and look for '+syntax'. Otherwise it could be your terminal emulator playing up. Try :set t_Co to see how many colours Vim can recognise in your terminal. Ideally this should return at least '8'. If it doesn't there may be some tips in :h xterm-color.