First we need to reference the Styles we want to use.

<link rel="stylesheet" href="[file path]/kendo.common.min.css" />
<link rel="stylesheet" href="[file path]/kendo.[Theme].min.css" />

Now most of the controls use the [Theme], given in the above Style Resource.

Some controls like Chart, TreeMap, Diagram, StockChart, Sparkline, RadialGauge, and LinearGauge are rendered with JavaScript computed Layouts and need some extra configuration at initialization.

For example the Chart:

$("#chart").kendoChart({
    theme: "blueOpal",
    //...
});

List of themes:

"black", "blueOpal", "bootstrap", "default", "flat", "highContrast", "material", "materialBlack", "metro", "metroBlack", "moonlight", "silver", "uniform", "fiori"(kendo ui pro), "nova"

To set them globally you are able to override Kendo this way:

//The Themable Elements
var themable = ["Chart", "TreeMap", "Diagram", "StockChart", "Sparkline", "RadialGauge", "LinearGauge"];

//Check if kendo.dataviz is available
if (kendo.dataviz) {
  
  //Set for each control the default theme
  for (var i = 0; i < themable.length; i++) {
    var widget = kendo.dataviz.ui[themable[i]];

    if (widget) {
      widget.fn.options.theme = "blueOpal";
    }
  }
}