Vitamin C . . .?

[Answer: If you're using KI solution, in a sense, the solution does not always turn blue for the endpoints of all titrations: it really depends on what the vitamin C came from (e.g.: foodstuffs, tablets, etc.). I did this experiment earlier this term and mine appeared brown instead of blue. However, back to your question. The endpoint would be DARK blue, dark enough that it doesn't get darker even if more solution was added for titration. Thus, you should titrate a small sample first, and then use that as your comparison for colour for the remainder of your titrations.]