Jupiter is the name of the new default cPanel theme, and one of the most hated things about the new theme is the new icon style:
To bring back the old icons from the Paper Lantern theme to Jupiter, simply copy the icons
cp -r /usr/local/cpanel/base/frontend/paper_lantern/styled/glass/icons /usr/local/cpanel/base/frontedend/jupiter/assets/application_icons
And run this script to regenerate sprite icons:
Woala, we got color again:
TIP: Because these icons get rewritten when Cpanel updates the Jupiter theme, you can add the above two lines of code to the cpanel upcp script so that even after every updated, the icons get re-added.