Set v-banner background color to card background

[tbra91]

I have a v-banner with the app property placed directly inside v-main to show a warning on top of scrollable content. The default background colour for this is transparent, so content is visible under the banner. Setting the color property allows me to set a color as expected, but ideally I want this banner to have the same colour as a v-card background for both light and dark themes.

I can achieve this by setting :color="$vuetify.theme.dark ? '#1E1E1E' : 'white', but what's the best way to get the card background color dynamically instead of hardcoding it like this?