No matter which of the free themes I am using, when setting the color using Settings → Branding, that color is applied to both light and dark mode.
For obvious reasons, that is not very user friendly. It would be great with an option for color for text, links and buttons for light and dark.
To further explain this; this image shows the areas where the accent color stays the same - no matter what free theme you use with light or dark “mode”. I have chosen to not show the subscribe button since I will add a contact us form button in its place.