I often see tips on clever ways of storing all those damned bobbins. Here’s a thought: don’t.
I have a handful of bobbins filled with my basic colours: black; white; navy; olive. I also have one for basting thread, which is usually the ugliest colour or crappiest thread in my collection. When these bobbins run out, I fill them up completely.
Then I have a few bobbins for current projects using something other than basic colours. When I’m done the project, if there’s any thread left on the bobbin I just wind it back onto the spool. It only takes a minute. I leave a longer tail on the rewound thread so I can tell easily which thread is on top. In the unlikely event that I’m starting a new project and there’s no free bobbin, I pick the bobbin that I’m least likely to use with the current thread, put the thread back on the spool, and load it with the new colour.
I only own about 10 bobbins, so storage is easy.