Checksumcolor

Context: In December 2013 a patch was proposed to the coreutils list to add a --color option to the commands md5sum and shaXsum to display the checksums in color to make it easier to visually identify similarities in a list of printed checksums. The patch was not accepted for inclusion and instead it was suggested to create a command line utility which can be used to pipe the output of the md5sum and shaXsum commands similar to the utility colordiff.

Task: The task is to create this command line utility that we can use to pipe the output of the md5sum and shaXsum commands and that colors the checksum part of the output. Take each group of 3 or 6 hexadecimal characters and interpret it as if it was a color code and print it with the closest console color. Print with colors if the output is the terminal or print the input unchanged if the output of the utility is a pipe.