How can I change the Essence's color scheme?

Add the below code to custom css (dashboard > appearance > customize > custom css) and make sure to replace the hexcode with your own choice of color code (from here).

Header Area

For Top bar:

#top-bar {
	color: hexcode;
	background: hexcode;
}

For navigation:

 #navigation {
	border-color: hexcode;
}

Navigation Panel hook & search icon:

#navigation-panel-hook, #navigation-search-hook {
	color: hexcode;
}

Small Carousel border (the small slide icons below the posts):

.carousel-wrapper .owl-theme .owl-controls .owl-page span {
	background: hexcode;
}

.owl-theme .owl-controls .owl-page span {
	background: hexcode;
}

Border below big carousel:

.vertical-carousel {
	border-color: hexcode;
}

Content Area

Category color & background:

.blog-post-cats a {
	background: hexcode;
	color: hexcode;
}

.blog-post-cats {
	border-color: hexcode;
}

Continue reading more button:

.blog-post-read-more a {
	background: hexcode;
	color: hexcode;
}

Share count color:

.blog-post-meta-share-count-num {
	color: hexcode;
}

Sidebar

Widget title:

#sidebar .widget-title {
	border-color: hexcode;
	color: hexcode;
}

About me section:

.about-author-widget {
	border-color: hexcode;
}