trying to create event listener using leaflet and javascript, how to change tectonic fault line color when user changes map base layer? not working?

// Create the map object with center, zoom level and default layer.
let map = L.map('mapid', {
    center: [40.7, -94.5],
    zoom: 3,
    layers: [streets]
});

// Create a base layer that holds all three maps.
let baseMaps = {
  "Streets": streets,
  "Satellite": satelliteStreets,
  "Night Navigation": nightNav
};

// 1. Add a 2nd layer group for the tectonic plate data.
let allEarthquakes = new L.LayerGroup();
let allTectonics = new L.LayerGroup();
let majorEQ = new L.LayerGroup();


// 2. Add a reference to the tectonic plates group to the overlays object.
let overlays = {
  "Earthquakes": allEarthquakes,
  "Tectonic Plates": allTectonics,
  "Major Earthquakes": majorEQ
};

// Then we add a control to the map that will allow the user to change which
// layers are visible.
L.control.layers(baseMaps, overlays).addTo(map);

let tectonicData = "https://raw.githubusercontent.com/fraxen/tectonicplates/master/GeoJSON/PB2002_boundaries.json";


  let tstyle = map.on('baselayerchange', function(feature) {
      console.log('base layer has been changed');
      return {
        fillColor: tecStyle(L.overlays),
        fillOpacity: 0.8,
        weight: 0.5
    };
  });

  function tecStyle(feature) {
    if (feature === baseMaps["Streets"]) { return "purple";
    }
    if (feature === baseMaps["Satellite"]) {
    return "red";
    }
    if (feature === baseMaps["Night Navigation"]) { 
    return "red";
    }
  };

  // 3. Use d3.json to make a call to get our Tectonic Plate geoJSON data.

  d3.json(tectonicData).then(function(data) {
    
    // Create GeoJSON layer with the retrieved data.
    L.geoJSON(data, {
      style: tstyle,
      onEachFeature: function(feature, layer){
        layer.bindPopup("<h3><b> Plate Boundary Name: " + feature.properties.Name + "</h3></b>");
      }
    }).addTo(allTectonics);
    allTectonics.addTo(map);
    
  });
});

I want the tectonic fault line color to change colors depending on whether the user is on the 'Streets', 'Satellite', or 'Night Navigation' layers. For example, I want the fault line color to be 'purple' when on 'Streets', 'red' when on 'Satellite', and 'blue' when on 'Night Navigation' base layer maps. I was hoping I could get it to work using map.on and the event listener is working, because it comes up in my DevTools console, but the color of the fault line remains the default color of 'blue' no matter what layer I am on. What am I doing wrong here? or is there an easier way to do this?