The program, grc, is "the frontend for generic colouriser grcat." The project exists at GitHub, but it might be installed from a repository, if your O/S has packaged the software. Many commands come preconfigured, and it can be customized to colorize any command.
A portion of output is shown below for the command, whois stackexchansssssssge.com.

To incorporate the caveat noted in the comments, please note that one can abbreviate the command, grc whois <arg>, with the command, whois <arg>, by sourcing the appropriate script that comes with the software. This script (one of grc.zsh, grc.bashrc, or grc.fish, according to the corresponding shell in use) establishes aliases for the configured commands that prepend each configured command with grc --colour=auto.
The software has preconfigured color for the following commands.
- cc
- configure
- cvs
- df
- diff
- dig
- gcc
- gmake
- ifconfig
- last
- ldap
- ls
- make
- mount
- mtr
- netstat
- ping
- ping6
- ps
- traceroute
- traceroute6
- wdiff
- whois
- iwconfig
Accomplish the Goal Without Color
In Linux, at least, note also that the exit code from whois should be 0 when a domain name was found and 1 when a domain name was not found.
whois stackexchange.com
echo $?
This produces an exit code of 0 - found.
whois stackexchansssssssge.com
echo $?
This produces an exit code of 1 - not found.
Or, to deduce the same with no output from whois, try as follows, using ; to assure output of the exit code.
whois stackexchange.com >&- ; echo $?
whois stackexchansssssssge.com >&- ; echo $?