I don’t know the yardage used, I tend to work in grams. My waitcoat used 260g; so I would think that if you were to buy or spin 6-7 50g balls in assorted colours you would have enough yarn to complete the waistcoat in the given size.

There is a detailed diagram in the pattern, giving all the measurments of the finished garment, so allthough the pattern is only written for one size, it should be fairly easy to calculate where to add or remove a few rows or stitches to make it up in a different size.