Vega Lite Fill and Stroke Encoding

fill_strok.vl.json

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "A scatterplot showing body mass and flipper lengths of penguins.",
  "data": {"url": "data/penguins.json"},
  "transform": [{"sample": 30}],
  "mark": "point",
  "encoding": {
    "x": {
      "field": "Flipper Length (mm)",
      "type": "quantitative",
      "scale": {"zero": false}
    },
    "y": {
      "field": "Body Mass (g)",
      "type": "quantitative",
      "scale": {"zero": false}
    },
    "strokeWidth": {"value": 4},
    "stroke": {"field": "Species", "type": "nominal"},
    "fill": {
      "field": "Flipper Length (mm)",
      "type": "quantitative",
      "scale": {"scheme": "greys"}
    }
  }
}