Combine > Color swatches
The Quick buy block is one of the places where product color swatches can be used. These will appear automatically if you choose to from the Theme Settings > Product card > Product variants area..
First, you need to define what color swatches labels are you using.. The defaults are some popular ones, such as color or colour, but you can use this feature for custom labels as well. For example, if you have a variant called Lipstick color, you can write lipstick color as an option in the color swatches label, and the theme will pick it up and transform the values in color swatches.
Now, Combine has built-in support for color swatches, based on color names, which use the web supported color names. However, there may be instances where a store would require more specific swatches with complex colors or patterns. In this scenario, you can upload images for your swatches, as the theme has the proper logic to detect custom images for custom swatches.
For any color swatch that you want to add, you just have to upload a 90x90px png file in your store's files section, with the name exactly the same as your product's variant handle.
For example, let's say that your product has a variant called "Dark Grey". You will want to create an image file name "dark-grey.png" and upload it into the Settings > Files section of your Shopify admin. That's it!