When ordering the right yarn for your project, you can compare the colors on your screen with the yarn colors in webshops or in your local yarn store.
Later on this year, it becomes possible to compare the colors from Stitch Fiddle directly to the yarn colors of the most commonly used brands.
There's no easy formula to calculate how much yarn you need. It depends in several different things. Search on Google to learn more about it: https://www.google.nl/search?q=how+much+yarn+do+i+need
Start now designing your own first pattern!