The Riddles specified they arrived in 1887... Anne Sullivan arrived to teach her 8 March 1887 and she learned about water "the following month" (April) so this would be the month the Riddles arrived. This means during the first visit that Helen was actually SIX years (plus ~10 months) old, as it was about 2 months prior to her seventh birthday.
Helen, as a child, is depicted with fair skin and brown hair tied in a bun. She wears a grey blouse with a red ribbon, a blue skirt, and dark blue flats.
Helen has no light in her eyes, unlike the other characters. This is probably to show that she is blind.