如何在vega中基于列突出显示适当的栏？

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A basic bar chart example.",
  "data": {
    "values": [
      {"category": "A", "value": 28},
      {"category": "B", "value": 55},
      {"category": "C", "value": 43},
      {"category": "D", "value": 91},
      {"category": "E", "value": 81},
      {"category": "F", "value": 53},
      {"category": "G", "value": 19},
      {"category": "H", "value": 87}
    ]
  },
  "mark": "bar",
  "encoding": {
    "x": {"field": "category", "type": "ordinal"},
    "y": {"field": "value", "type": "quantitative"},
    "color": {"field": "category", "type": "nominal"}
  }
}