For dev - How to use Hex color for Swatch filter option
By default, you need to upload each image which is corresponding with each filter option value (as instructed in this guide). If you are familiar with CSS, you can use Hex color to display the Swatches.
Instruction
.boost-pfs-filter-option-item-list-swatch span.boost-pfs-filter-option-swatch-image[title="Jet Black"] {background-color: #111111 !important;}