I'm going to create a new icon theme for Libreoffice (a word processing application that runs on Windows, Mac and Linux), but I still need to make some decisions regarding the style of the icons. The biggest question I have right now is should the icons be monochrome or should they be colorful?
The advantage of monochrome icons is that they usually have good visual uniformity and the lack of color keeps them from being distracting. Monochrome icons are also used in Google Docs and are encouraged by Google's Material design and the Windows 10 UWP design.
The advantage of colorful icons is that because they are colorful, the color gives the user an additional context clue for them to be recognizable. The icon set in Microsoft Office contain some colorful icons. Colorful icons are recommended in the HIG guidelines for Windows 7 and the HIG guidelines for OS X.
I'm leaning towards using flat colorful icons. Thoughts, suggestions, questions?
EDIT: I found this article which discusses this issue, using Libreoffice as an example.