If you select emphasis color the text color will change. The colors available vary with different themes.
This text box has an image selected for the background color.
When a lighter image is selected the text color reverts to black.
<h1 style="color:blue;">This is a Blue Heading</h1>
<p style="color:green;">This is done by <b style="color:red;">embedding</b> code in the Embed function.</p>
To highlight background color also:
<p style="color:green;">This is done by <b style="color:red;background-color: yellow;">embedding</b> code in the Embed function.</p>
This in not a very user friendly method, but it is a way of accomplishing it until text color options are added to New Sites.
Inline CSS: https://www.w3schools.com/html/html_css.asp