OTOH I just learned that green and orange in the Irish flag stand for Catholics and Protestants respectively, while in the Ivory Coast flag, they symbolize some run-of-the-mill cliches. So now I'll know that when I see Catholics first, it's Ireland, and when I see “color of rich and generous earth”, that's Ivory Coast.
The best way to learn is really to combine both: make once the effort to build a mnemonic for things that you don't remember easily or which you expect might end up confusing - and then use anki to reinforce this memory.
Our brain works with connections, and connections take effort to form, so all you do to form a single personal mnemonic by definition helps you build these connections, with the mnemonic then helping you later to again find this chain of neural connections that means 'flag of ireland'.