Single/multi-choice problem: Which of the following solutions is better for the following goal:
How can you identify often used key's quickly?

Choose from:
[+] Paint the key with fingernail polish to color code -or even label with the name if you choose..
[+] Paint the door lock with fingernail polish to color code -or even label with the name if you choose..
Paint the key with fingernail polish to color code -or even label with the name if you choose.