pgcrypto : how to get SHA1(string) as a 40-char string, NOT binary string?

I have the contrib/pgcrypto installed.
I want to get the 40-character hash from SHA1

Example: SELECT digest('blue', 'sha1') would be:
4c9a82ce72ca2519f38d0af0abbb4cecb9fceca9

I was surprised and disappointed to get a binary-hash back.

Does anyone know how to get the regular 40-character string back from
SHA1 instead of the binary-hash?   (Or how to convert a binary-hash
into a-z0-9 chars?)