{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
  "elmType": "div",
  "style": {
    "color": "#fff",
    "padding-left": "10px",
    "background-color": {
      "operator": "?",
      "operands": [
        {
          "operator": ">=",
          "operands": [
            "@currentField",
            "[$ProjectBudget]"
          ]
        },
        "#e81123",
        "#00B294"
      ]
    }
  },
  "children": [
    {
      "elmType": "span",
      "txtContent": "£",
      "style": {
        "display": "inline-block",
        "padding": "0 1px"
      }
    },
    {
      "elmType": "span",
      "txtContent": "@currentField"
    }
  ]
}