Each taxicab shall bear on the outside of each rear door, in painted letters not less than four inches nor more than six inches in height, the name of the owner or cab company and in addition, may bear an identifying design, approved by the Legislative Authority. No taxicab shall have a color scheme or identifying design, which in the opinion of the Legislative Authority, conflicts with or imitates any color scheme or identifying design used on vehicles already operating under this chapter, in such a manner as to be misleading or tend to deceive or defraud the public.