Collection swatches need both the Collection widget installed in your theme and the relevant product groups or variant swatches configured for collection display.
First, enable the collection app embed in the theme you are using. Then follow the instructions for your product setup below.
For separate products linked in a group
Open the group in Product groups.
Expand Advanced.
Set Displayed on to Product and collection widget, or Collection widget if you want the group only on collection cards.
Select Save.
If the group is managed by an automation, check the automation's display settings too when changing how its groups should be created or maintained.
To choose which group options appear on collection cards:
Open Settings > Product groups.
Find Collection display.
Select the option names you want under Which option names to show in collection swatches?
Select Save.
For example, you can show Color on collection cards while keeping Fit visible only on product pages. This setting applies to product-group options with those names, not to variant options.
For variants within one product
Open Variant swatches.
Under Status, choose Enabled, or Only selected products with the intended products selected.
Set Displayed on to Product and collection pages or Collection pages only.
Choose Color or image or Variant image as the Swatch Style for the option you want to show.
These selections save automatically. For Color or image, select Configure to assign any missing colors or images, then select Save.
Collection cards show a visual variant option. Options using Pill / Button, such as a text-only Size option, are not shown as variant swatches on collection cards. If several options use a visual style, the first eligible option in the product's option order is used.
If swatches appear on products but not collections
Check the collection embed in the theme you are viewing, then the display settings above. Product-page installation and display settings are separate from collection display.
Also check:
For groups, the collection card's product must belong to a group configured for collection display.
For variants, the product must be included if you chose Only selected products.
Hidden inactive or sold-out products can reduce the visible swatches. See Control sold-out and inactive swatches.
Allow saved changes to finish syncing, then refresh the page.
If swatches are still missing, or appear inconsistently after filtering or loading more products, send support the collection URL, theme name, and the steps that make them disappear. The card layout or another app may need investigation.