Since there is no support for a ternary operator, I'm trying to use the yes_no modifier instead. I'm new to Statamic and Antlers, so not sure exactly how to accomplish this:

<?php
    echo isset($color) ? $color : '#000';

But it seems that (from the docs) I can only output string literals with the yes_no modifier: https://docs.statamic.com/modifiers/yes_no

{{ color | yes_no:color:"#000" }}

where "color" is a field — the above doesn't do anything.