Within the theme settings for the ShowTime theme, there are options to choose heading and text colors for Content headings and text as well as Regular headings and text. Please see the image below for a description of what these settings refer to.
The Content heading and text options pertain to text that shows outside the white container boxes. This includes things like the page title, breadcrumb, and some elements on the home page. The color you choose here should contrast with your chosen background color.
The Regular heading and text options pertain to text that shows within the white content containers.