This should use more striking shades of red or green for such a narrow bar or a wider bar so that the colour stands out more. A wide, black line between the two parts of the bar to delimit the coloured regions would help too.
Or, just pick some colours that aren't so commonly affected by colour blindness. I think most (if not all) such bars also have the percentage written nearby, but having the bar work for everyone isn't essential - the number of people with non-red-green colour blindness is probably small enough that we don't need to go out of our way to cater to them (as long as no information is only available through the colours).