Question: when did indigo become a color of the rainbow
[{'answer': 'In the mid-1660s', 'provenance': [{'wikipedia_id': '15250', 'title': 'Indigo', 'start_paragraph_id': 12, 'start_character': 76, 'end_paragraph_id': 12, 'end_character': 92, 'bleu_score': 1.0, 'section': 'Section::::Classification as a spectral color.\n'}]}, {'provenance': [{'wikipedia_id': '15250', 'title': 'Indigo', 'start_paragraph_id': 12, 'start_character': 0, 'end_paragraph_id': 12, 'end_character': 1020, 'bleu_score': 0.988538208695211, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18359656224011597245}, 'section': 'Section::::Classification as a spectral color.\n'}]}]