Appearances are often deceiving

काकः कृष्णः पिकः कृष्णः
को भेदः पिककाकयोः ।
वसन्तकाले सम्प्राप्ते
काकः काकः पिकः पिकः ॥

- कुवलयानन्दः

Crow is black, and so is a cuckoo. But then, what is the difference between the two? With the arrival of spring, (we realize that) a crow is just a crow, and a cuckoo is a cuckoo indeed.

Appearances are deceptive.
Do not judge a book by its cover.