Whether your doing r/r on top and w/w bottom or r/w top and r/w bottom. They both will have the same impact as in your post your doing a X pattern. So everyone is right as long as there clear lenses unless ther colored then your preference.
That way you have one solid color of red and then one solid color of white. It will be more effective becuase if you flash a red and white at a close enough proximity it will appear pink to an extend. Just my opinion but i think this way the drivers will see them better and there will be no question of what color the light is.