JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.js"></script>
<div id="infopane">click on a marker</div>
<div id="map"></div>

CSS

#map {
  height: 360px;
  width: 49%;
}

#infopane {
  width: 49%;
  float: right;
  border: 0.2px solid #c0c0c0;
}

h2 {
  margin-top: 0.1em;
  margin-left: 0.1em;
  font-family: Arial, Helvetica, sans-serif;
}

JavaScript

// uses http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css
// uses http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.js


var map = L.map("map").setView([51.52, 11], 8);

L.tileLayer('http://{s}.tile.osm.org/{z}/{x}/{y}.png', {
  attribution: 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, <a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>'
}).addTo(map);

var loadGIST = function() {
  $.ajax({
    url: "https://gist.githubusercontent.com/anonymous/e54a23c4d5204d7ea8c1/raw/a9559d405c30630caccc4a59c26e20a2d44f3d6e/map.geojson",
    /*jsonp: "callback",*/
    dataType: "json",
    success: function(data, status, xhr) {
        jsonLayer.addData(data);
      } // end success
  });
};

var selectedFeature = null;

var styleForFeature = function(feat) {
  // style for not selected features
  sty = {
    "color": "green",
    "fillColor": "green",
    weight: 5
  }
  if (feat.properties.delta_18_O == "yes") {
    sty.color = "green";
  } else {
    sty.color = "blue";
    sty.fillColor = "blue";
  }
  return sty;
}

//will be filled with data from ajax request
var jsonLayer = L.geoJson(null, {
    onEachFeature: function(f, layer) {
      layer.on('click', function(e) {
        $("#infopane").html("<h2>" + e.target.feature.properties.name + "</h2>" + "Monitoring of Delta 18 O: " + e.target.feature.properties.delta_18_O + "<br>" + "Monitoring of dripwater: " + e.target.feature.properties.drip_water + "<br>");
        selectedFeature = e.target.feature;
        redrawLayerMarkers();
      });
    },
    pointToLayer: function(feature, latlng) {
      return new L.CircleMarker(latlng, {
        radius: 7,
        fillOpacity: 0.85
      });
    },
    style: styleForFeature
  })
  .addTo(map);

//jsonLayer.addData(fc);

loadGIST();

var redrawLayerMarkers = function() {
  jsonLayer.eachLayer(function(l) {
    if (l.feature == selectedFeature) {
      l.setStyle({
        color: 'yellow',
        weight: 7
      })
    }...