I suspect this is a bug, but happy to be corrected. Using latest versions of plugin, theme and WP.
1. Create a Container.
2. Go to colours of that Container and set the background colour to red and the text colour to yellow.
3. Add a Paragraph block to the container and type “Hello”
4. Add a Headliner block below the Paragraph block but inside the Container and type “World”
5. The live editor will show both words in yellow font. So far so good.
6. Click on Update and only Hello is in yellow. World is in black.
I would have expected both words to be rendered in yellow.