The specific yarns I used to make my samples are just included in the pattern for reference. Yarns are often altered and discontinued by manufacturers, and, particularly if the pattern is a few years old, you may not be able to find the exact same yarns I used. Contact the manufacturer for assistance if you’re looking for a specific yarn (here are the websites for the brands I usually use for amigurumi: Bernat, Red Heart, Lion Brand).
However, my patterns are designed to work in any yarn (provided you choose an appropriately-sized hook for your yarn – see my Resizing Amigurumi article for details). See also How do I choose/substitute yarn? for helpful advice on choosing a substitute yarn.
Note: For patterns that use many different colours of yarn but the exact shades aren’t important (e.g. a plant pattern where you can choose to make all the components in different shades and they’ll still look great) I may just list the yarn names in the pattern, and not all the exact shades I used. If you’d like a complete list of the specific yarn colours I used for a pattern, I always try to list them in full in my project listing for that pattern in the Ravelry database, so you can look there. (If you find my rav project is missing those details, please let me know so I can add them!)