I used to buy all different colors but guess what? I still have most of them. I use whites and neutrals almost all the time.
I have several machines and 5-10 bobbins for each I think.
I love my side-winder! I bought it mainly for my vintage machines b/c it's just easier for me to wind a bunch at once.
But I use it for all of them now.
I never heard of oiling one. For the money I would just get another with a Joann's coupon if mine croaks.