apply 24bit color workaround only if needed

.vimrc

@@ -89,8 +89,10 @@ let g:syntastic_check_on_wq = 0
 
 " 24bits color fix for tmux
 " inspiration from https://github.com/vim/vim/issues/3608
-let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
-let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
+if !has('gui_running') && &term =~ '^\%(screen\|tmux\)'
+    let &t_8f = "\<Esc>[38;2;%lu;%lu;%lum"
+    let &t_8b = "\<Esc>[48;2;%lu;%lu;%lum"
+endif
 
 " solarized config
 set termguicolors