Active radios hidden on Paper with color="secondary"

[vhscom]

Describe the bug
When I add radio buttons as a child to Paper with color="secondary" the active radio button is not visible.

To Reproduce
Steps to reproduce the behavior:

1. Install deps npm i -D @smui/paper @smui/form-field @smui/radio
2. Drop code below into a +page.svelte document.
3. View the document.
4. Observe the active radio is not visible.

<script>
  import Paper from '@smui/paper';
  import FormField from '@smui/form-field';
  import Radio from '@smui/radio';

  let selected = 'total price';
</script>

<Paper color="secondary" variant="unelevated" class="content-wrapper">
  {#each ['total price', 'per credit price'] as options}
    <FormField>
      <Radio bind:group={selected} value={options} />
      <span slot="label">{`${options[0].toUpperCase()}${options.slice(1)}`}</span>
    </FormField>
  {/each}
</Paper>

Expected behavior
Active radio should be visible on Paper using secondary color.

Screenshots
https://github.com/hperrin/svelte-material-ui/assets/97140109/a24ad19a-9495-4c26-9ea3-fd59daa88b1f

Desktop (please complete the following information):

• OS: [e.g. iOS] macos
• Browser [e.g. chrome, safari] Chromium
• Version [e.g. 22] Version 117.0.5938.92 (Official Build) (arm64)

Additional context
Bug created from newly scaffolded Svelte project using the SMUI v7 beta 15 release. On a related note the documentation website uses a Card to display radio examples. It's not possible to reproduce this issue using a Card because, although Card accepts a color attribute the attribute when set to color="secondary" does not change the color of the card.