When we receive a shipment of rugs, we also receive a generous supply of the yarn that was used in making them, so that we maintain a huge selection of colors for future repairs. In cases where we do not have an exact match, we are experts at mixing dyes and matching existing colors.
Ever wonder why some rugs have a lot of 'loose threads' on the underside?
These were intentionally left in place by the weavers, so that matching threads would be available for years into the future for any needed repairs!
When you make something that is intended to be used for centuries, you tend to think ahead...