I still wind different colors onto my 301 bobbins. I only have 4 good ones so sometimes I have 2 - 3 colors on a bobbin. It is a wee bit crazy but have not found any good replacement bobbins although I know there are shops that sell them. However, I have been burned by buying bobbins from 2 reputable dealers and the darn bobbins don't work so am out teh $ spent on them and the shipping.
What I have are some possibly vintage bobbins with one side with 4 holes and one side with no holes that aren't class 66 or class 15 ones. Anybody want to take a guess??