The level system doesn't actually sort red hair into a specific category, though Tang said many redheads can fall under level six as well. This means that, like brunettes, people with red hair would have to lift their hair colour at least a few levels to get to a blond colour. Again, you may have to see your colourist a few times to get to your desired shade of blond, so be patient.
In the same phased approach, adding highlights to your hair may also be worth considering when going from red to blond, since the highlights will make the contrast look less harsh when your natural colour begins to grow back out.