tumultuary definitely see if one of their oranges work for you then cuz that would be simplest. They also have a link in their description where you can request a new color.
If you want to essentially combine the material black mango folders with papirus app icons on your own, then it's gonna be a bit hacky. There could be better ways to do this, but here's what I've done in the past:
- if not already, make an 'icons' directory at ~/.local/share/icons
- copy existing papirus theme to a custom theme name in the local/share/icons directory (ie. from /usr/share/icons: sudo cp Papirus-Dark ~/.local/share/icons/Material-Black-Papirus)
- [hacky part] - remove all folder icons from Material-Black-Papirus
- edit index.theme file in your custom theme and add Material-Black-Icons to the "Inherits" line (ie. Inhertis=Material-Black-Icons). This should pull in any missing folders/icons from Papirus in from Material-Black (ie. the Papirus folders we just removed).
Been awhile since I've done this, but that's the gist of it from what I recall.