What is the best way to organize keys on keyrings?

I have a lot of keys to keep up with. I need the best way to identify them and organize them. These are not to hang on a key holder, but rather must be carried in my purse. I have at least 20. [Vehicle keys are not a problem and are kept separate.]

I see colored keys, keys with colored tops, a colored plastic thing that go over the top of the key, cardboard disks that you write on, etc.

For example, here is some of what I have: keys to my house, storage building, utility box access, file cabinet, garage door, post office box. At my mother’s: 5 different exterior door keys, utility shed key, file cabinet key, desk key, garage door keys, post office box key, lawnmower key.

I need a way to clearly label them (label or words must not wear off) and a way to organize them, by color, on rings or something.

Any help appreciated. Thanks in advance.