Before revision: Thus if I know that someone means to explain a colour-word to me the ostensive definition "That is called ' sepia ' " will help me to understand the word.... One has already to know (or be able to do) something in order to be capable of asking a thing's name.
After revision: Thus if I know that someone means to explain a colour-word to me the ostensive definition "That is called ' Sepia (color) ' " will help me to understand the word.... One has already to know (or be able to do) something in order to be capable of asking a thing's name.