Group by header color depending on item count

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/row-formatting.schema.json",
  "groupProps": {
    "headerFormatter": {
      "elmType": "div",
      "style": {
        "padding": "4px 8px 5px 8px",
        "border-radius": "6px",
        "margin": "1px 4px 4px 1px",
        "background-color": "=if(@group.count == 1, 'Red',if(@group.count == 2, '#FF681E',if(@group.count == 3, '#FF980E',if(@group.count == 4, '#ffe40e','Green'))))"
      },
      "children": [
        {
          "elmType": "div",
          "txtContent": "=@group.count",
          "style": {
            "padding": "5px 5px 5px 5px",
            "color": "white",
            "font-weight": "500"
          }
        },
        {
          "elmType": "div",
          "txtContent": " of 5 ",
          "style": {
            "color": "white",
            "font-weight": "500"
          }
        }
      ]
    }
  }
}