here is a rough, general approach, with a few code examples (using jQuery/javascript):

1. Set up a couple of color styles for the markers (using circle markers here)

   var blueMarker = {
     radius: 8,
     fillColor: "#0000ff"
   };
   
   var redMarker = {
     radius: 8,
     fillColor: "#ff0000"
   }
   

2. Add the geojson features as L.circleMarkers, keeping track of each as a layer for color change. (Assuming here your feature properties have a "name" attribute; change as needed)

   var layerlist = {};  
   L.geoJson(data, {
     pointToLayer: function (feature, latlng) {
       return L.circleMarker(latlng, blueMarker);
     },
     onEachFeature: function(feature, layer) {  
       layerlist[feature.properties.name]=layer;  
     }
   }).addTo(map);  
   

3. Get the feature name from the input text box

   var name = $(input).val();
   

4. Remove the layer by name

   map.removeLayer(layerlist[name]);
   

5. Add the layer by name, and restyle

   layerlist[name].addTo(map).setStyle(redMarker);
   

here is a rough, general approach, with a few code examples (using jQuery/javascript):

1. Set up a couple of color styles for the markers (using circle markers here)

   var blueMarker = {
     radius: 8,
     fillColor: "#0000ff"
   };
   
   var redMarker = {
     radius: 8,
     fillColor: "#ff0000"
   }
   

2. Add the geojson features as L.circleMarkers, keeping track of each as a layer for color change. (Assuming here your feature properties have a "name" attribute; change as needed)

   var layerlist = {};  
   L.geoJson(data, {
     pointToLayer: function (feature, latlng) {
       return L.circleMarker(latlng, blueMarker);
     },
     onEachFeature: function(feature, layer) {  
       layerlist[feature.properties.name]=layer;  
     }
   }).addTo(map);  
   

3. Get the feature name from the input text box (not a plugin here, just regular html form input)

   // on change or submit
   var name = $(input).val();
   

4. Remove the layer by name

   map.removeLayer(layerlist[name]);
   

5. Add the layer by name, and restyle

   layerlist[name].addTo(map).setStyle(redMarker);