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;
}