The ringbearer traditionally wears an outfit to compliment the flower girl, and sometimes will match the groom. If your question is should another small boy wear ivory if walking next to the ringbearer I would say that the other boy should wear what your groomsmen are wearing.
If the ring bearer is walking down the aisle with an adult I also agree that the adult should be wearing the same as the groomsmen. Lori of ModelBride.com http://www.modelbride.com