It's inline CSS added directly by the ProfileBook plugin. If you want to adjust the styling simply add your CSS to the bottom of your Joomla template CSS file and if necessary you can override styles by adding !important tag (e.g. color: red !important;). At any rate it's located in the below file in the cbpbCssOutput function.
components/com_comprofiler/plugin/user/plug_cbprofilebook/cb.profilebook.php