Use gradient colour on font heading

Is it possible to apply gradient on headings?

Yes, very much possible with CSS3, however you need to use custom code for this.

Please take a look at this article Gradient Text | CSS-Tricks - CSS-Tricks

You will need something like this (change the color hex codes and class name):

.my-element-class {
  background: -webkit-linear-gradient(90deg, #eee, #333);
  background: -moz-linear-gradient(90deg, #eee, #333);
  background: -o-linear-gradient(90deg, #eee, #333);
  background: -ms-linear-gradient(90deg, #eee, #333);
  background: linear-gradient(90deg, #eee, #333);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}