@login_required
def color_form(request):
    if not request.user.groups.filter(name='color'):
        if request.user.has_perm('users.can_change'):
            return render_to_response('color/denied2.html')
        return render_to_response('color/denied.html')

    if request.method == 'POST':
        form = ColorForm(request.POST)
        if form.is_valid():
            return redirect('color_done')
    else:
        form = ColorForm()

    ...