What's wrong with this picture?
I needed a bobbin in a particular colour for my quilting, and I have none spare to wind. Ug. I don't like winding a different colour over the top of a half-full bobbin because inevitably I'll need the colour underneath, and that's just a straight path to frustration-ville.
So what I usually try to do is keep plenty of empty bobbins. But how do I do that without wasting thread? Well, I use my bobbins as thread spools when I'm piecing or sewing something that doesn't need a particular colour.
You just pop your bobbin onto your thread spool holder and use as usual. Easy!
I try and kind of match my colours to my piecing, like darks for darks and lights for lights, because you will see bright yellow piecing thread if you use it for midnight blue fabric. But I seem to use an awful lot of beige, grey, taupe and cream threads in my bobbins. And sage green, lavender and medium blue are pretty neutral too.
And have you ever made 'frankenbatting'? That's a term coined by (I'm pretty sure, correct me if I'm wrong) Pam from Hip to be a Square. It's where you piece together lots of random batting leftovers to make one bigger bit. And ain't nobody going to know if you did that with leftover lavender thread from your bobbin!
I don't use my bobbins when I'm quilting, because a) I'm going to run out of thread too quick and b) I don't know if having unwound from a spool and re-wound onto a bobbin would mess with my tension. But I've never had any problems using it for piecing, so give it a try.
And while we are on the topic of bobbins. I wanted to tell you about the best bobbin cases I've found. One of mine is a Sew Mate Bobbin Box, the other is exactly the same but unbranded. The inner is closed cell foam and the bobbins kind of squash in. They never fall out, they never unravel, the lid has a good catch and the hinge has never broken on me. The plastic is the same as plastic food storage containers, which means it doesn't smash if you drop it (ask me how I know).
Whenever I see them, which is infrequently in New Zealand for some reason, I buy them because people always want them when they see mine!