Why semicolons are lovely and colons less so

I am extremely good at memorizing esoterica, often serving as a walking password manager at various jobs I’ve held. Yet I never managed to keep more than a half dozen Alt-codes in my head when I used Windows full-time in the workplace. If you have a mnemonic for distinguishing between Alt-0159 and Alt-0161, I’d love to hear it. (But I bet you still remember my explanation of how to type *, •, and ° on a Mac from a few comments ago.)