Changing font weight on the widget-'headline' and color …

Running latest WP and theme ver. at https://www.fleksjobbernetvaer - How do I make the 'headline' bold or even change thier colors? Is it in the build in cuztomizer or? By headline I mean the widget headline (see screenshot, and look e.g. for "Flere sider...") https://snag.gy/iTQ24D.jpg thanks Knud