Customize Pivotal Tracker with a couple of extensions (in comment)

user-styles-pivotal-tracker.css

* {
	font-family: "Avenir-Medium" !important;
}

button[data-aid='AddButton'] {
	/*background-color: #87898A !important;*/
	background-color: #0078FF !important;
	background: linear-gradient(274deg, rgba(0,120,255,1) 29%, rgba(0,149,255,1) 67%, rgba(0,200,255,1) 100%) !important;
	padding: 3px 10px 2px !important;
	border-radius: 20px !important;
	font-size: 12px !important;
	font-weight: 900 !important;	
}

button[data-aid='AddButton']:hover {
	/*background-color: #DC7536 !important;*/
	/*background-color: #0078FF !important;*/
	background: linear-gradient(274deg, rgba(0,120,255,1) 29%, rgba(0,149,255,1) 67%, rgba(0,200,255,1) 100%) !important;
}

button[data-aid='AddButton']::before {
	content: "🧨   " !important;
}

button[data-aid='AddButton']  .MuiButton-startIcon {
	display: none !important;
}

.manual_planning_indicator {
	margin-top: 2px !important;
	padding-top: 1px !important;
}

.story .model, .story > .preview {
	border-top: none !important;
	border-bottom: none !important;
}

.story > .preview {
	border-top: dotted 1px rgba(0, 0, 0, 0.1) !important;
	border-bottom: none !important;
	/*padding-bottom: 4px !important;
	padding-top: 3.5px !important;*/
}

.story.release .preview {
	background-color: #34495e !important;
}

.tc_page_header {
	background-color: #444 !important;
}

/*.MuiListItem-root.Mui-selected {
	
  border-left-color: #8AC7FF !important;
	text-shadow: none !important;

	font-weight: 900;
}*/

.locator {
	border-top-color: transparent !important;
}

.preview .selector:before {
	opacity: 0.45 !important;
}

.preview .selector.selected:before {
	opacity: 1.0 !important;
}

/*.layouts .story .preview .parens {
	display: none !important;
}*/

.layouts .story .preview .parens:before {
	content: "[" !important;
}

.layouts .story .preview .parens:after {
	content: "]" !important;
}


.state.button { 
	/*margin-top: 4px !important;
  margin-bottom: 4px !important;*/
	border-radius: 2px !important;
	border: none !important;
	text-transform: uppercase !important;
	padding: 2px 3px 1px !important;
}

.state.button.start {
	font-style: italic !important;	
}

.preview .reveal.button {
	margin-top: 4px !important;
	border-radius: 2px !important;
	text-transform: uppercase !important;	
}

.label.std {
	/*font-family: "Avenir Next Condensed" !important;*/
	font-weight: 700 !important;
	font-style: italic !important;
	margin-left: 4px;	
}

.preview .name .label:not(:last-child):after {
	content: " " !important;
}

.preview .name .label {
	opacity: 0.95 !important;
}

.preview .selector { 
  border-left: none !important;
}

/*.layouts .story .preview .parens {
	display: none !imporant;
}*/

.tracker_markup {
	font-family: 'Avenir-Medium' !important;
}

.tracker_markup strong { 
	font-weight: 900 !important;	
}

.iteration .preview { 
	border: none !important;
}

/*aside.sidebar { 
	box-shadow: none !important;
}

.panel, .panel .container {
	border: none !important;
	margin: 0 !important;
}

.panel .container > header.draggable {
	border-radius: 0 !important;
}*/

Use this extension to apply these styles:
https://chrome.google.com/webstore/detail/styler-pro/hbhkfnpodhdcaophahpkiflechaoddoi

Use this extension to further style your labels:
https://chrome.google.com/webstore/detail/pivotal-labels/njkofaephafobbeabnmmmijchhhdomio

They're both open source:
https://github.com/lukestateson/styler-chrome
https://github.com/di/pivotallabels