"iron blue" meaning in English

{
  "forms": [
    {
      "form": "iron blues",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "iron blue (plural iron blues)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Blues",
          "orig": "en:Blues",
          "parents": [
            "Colors",
            "Light",
            "Vision",
            "Energy",
            "Senses",
            "Nature",
            "Perception",
            "All topics",
            "Body",
            "Fundamental",
            "Human"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "Any of several blue pigments, but especially Prussian blue or Turnbull's blue."
      ],
      "id": "en-iron_blue-en-noun-cFDn4CUW",
      "links": [
        [
          "pigment",
          "pigment"
        ],
        [
          "Prussian blue",
          "Prussian blue"
        ],
        [
          "Turnbull's blue",
          "Turnbull's blue"
        ]
      ]
    }
  ],
  "word": "iron blue"
}

{
  "forms": [
    {
      "form": "iron blues",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "iron blue (plural iron blues)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "en:Blues"
      ],
      "glosses": [
        "Any of several blue pigments, but especially Prussian blue or Turnbull's blue."
      ],
      "links": [
        [
          "pigment",
          "pigment"
        ],
        [
          "Prussian blue",
          "Prussian blue"
        ],
        [
          "Turnbull's blue",
          "Turnbull's blue"
        ]
      ]
    }
  ],
  "word": "iron blue"
}