Duration is hidden in Powershell on Windows with standard background color
What were you expecting to happen? The duration to be visible.
What actually happened? Duration is in the same color as powershells standard background color, so it is not visible.
With the --no-color flag

With color

Using the same color as the taskname would solve it.
Please post a sample of your gulpfile (preferably reduced to just the bit that's not working) N/A
What version of gulp are you using? Version v4.0.0
What versions of npm and node are you using? NPM v6.5.0 Node v10.14.2
Duplicate of https://github.com/gulpjs/gulp-cli/issues/63 and https://github.com/gulpjs/fancy-log/issues/18
This is a WIP but we don't have an ETA.
Could a quick solution be to change it to the same shade of blue as the task name "JsCompile"? That way it would be visible in powershell out of the box.
It's not just with the default PowerShell window colors. I modified my colors, and the duration is still invisible (with [email protected]).

Support for theming timestamps and messages was added to gulp-cli in https://github.com/gulpjs/gulp-cli/pull/260. This will be released as gulp-cli v3.0.0 and included in the gulp v5 release. As with all gulp-cli releases, newer versions can run older gulp so you'll be able to theme anything with v3.0.0