Template:New collapse/styles.css

/* increase specificity */
.new-collapse.new-collapse > .mw-collapsible-toggle {
	color: #0645ad;
	font-weight: bold;
	background: none;
	background-size: 1.27em;
	background-repeat: no-repeat;
	background-position: left center;
	padding-left: 1.77em;
}
.new-collapse.new-collapse > .mw-collapsible-toggle-collapsed {
	background-image: url(https://upload.wikimedia.org/wikipedia/commons/a/a1/OOjs_UI_icon_caretDown.svg); /* [[File:OOjs_UI_icon_caretDown.svg]] */
}
.new-collapse.new-collapse > .mw-collapsible-toggle-expanded {
	background-image: url(https://upload.wikimedia.org/wikipedia/commons/1/1b/OOjs_UI_icon_caretUp.svg); /* [[File:OOjs_UI_icon_caretUp.svg]] */
}