Toggle between colorschemes on vim

let g:focuscolour = 0

function! ToggleFocusColor()
  if (g:focuscolour)
    colorscheme desert
    let g:focuscolour = 0
  else
    colorscheme focus-dark
    let g:focuscolour = 1
  endif
endfunc

"Set F6 to toggle
nmap <silent> <F6> :call ToggleFocusColor()<CR>