The Separator component contains improper CSS styling when a color has not been set for the component (see screenshot).
STEPS TO REPRODUCE
1. Add a content type page.
2. Add Separator component.
3. Inspect component through browser dev tool.
Border-color should not exist as no color has been set for the component (see
Border-color exists and has no value (see screenshot).
The issue only occurs when the color has not been set for the component.
This issue also occurs in other fragment components that use color palettes (in particular, the Heading and Paragraph components).