Let me start by saying....NO.....
You use whatever yarn tickles your fabric fancy...meaning, you knit some and if you like it ...use it...
Unless, of course, you have a gauge to go by for a fitted item..then you need to hit gauge with the yarn and whatever needle will do the trick.
The yarn ball label gives you a jumping off point to start with. It is the needle that is
recomended to use with that yarn. It is not the needle that you HAVE to use with that yarn.
Same goes with the patterns, they give you a
recomended needle, the one that the pattern writer used. Not neccesarily the one that YOU will use.
I started a pattern yesterday and started swatching with my usual 2 needle sizes up and was shocked to find that I actually hit gauge with the recomended needle size! This is a rare occation.
