"royal blues" meaning in Anglais

{
  "categories": [
    {
      "kind": "other",
      "name": "Formes de locutions nominales en anglais",
      "parents": [],
      "source": "w"
    },
    {
      "kind": "other",
      "name": "Anglais",
      "orig": "anglais",
      "parents": [],
      "source": "w"
    }
  ],
  "lang": "Anglais",
  "lang_code": "en",
  "pos": "noun",
  "pos_title": "Forme de locution nominale",
  "senses": [
    {
      "form_of": [
        {
          "word": "royal blue"
        }
      ],
      "glosses": [
        "Pluriel de royal blue."
      ],
      "id": "fr-royal_blues-en-noun-CIx-rBXY"
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "royal blues"
}

{
  "categories": [
    "Formes de locutions nominales en anglais",
    "anglais"
  ],
  "lang": "Anglais",
  "lang_code": "en",
  "pos": "noun",
  "pos_title": "Forme de locution nominale",
  "senses": [
    {
      "form_of": [
        {
          "word": "royal blue"
        }
      ],
      "glosses": [
        "Pluriel de royal blue."
      ]
    }
  ],
  "tags": [
    "form-of"
  ],
  "word": "royal blues"
}