Quoting colon in ansible

I am trying to use ansible to check that the output of a particular program is set to a certain value. That value includes a colon followed by a space, and this seems to register as a syntax error no matter how I quote it.

example:

---
- hosts: all
  tasks:
    - raw: echo "something: else"
  register: progOutput

- debug:
    msg: "something else happened!"
  when: progOutput.stdout_lines[-1] != "something: else"

When I run this, I get an error on the first 'raw' command:

ERROR! Syntax Error while loading YAML.


The error appears to have been in '<snip>/test.yml': line 4, column 27, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:

  tasks:
    - raw: echo "something: else"
                          ^ here

(naturally, my actual use case involved a real program that had a colon in its output, not 'raw: echo'. This was nevertheless the error I saw.)

Clearly, quoting the string in question doesn't fix the problem. I also tried escaping the : with a backslash (\).