File labels in Nautilus are not properly themed

[Amr Ibrahim]

Steps to see the bug
1. Open Nautilus and change zoom to default 100%
2. Go to the app settings
3. Select any three labels to show under file icons

The labels should be light grey, not black like the file name. See the attached screenshots.

Yaru
https://user-images.githubusercontent.com/45657128/77167618-a8fd8300-6ab6-11ea-819d-6737c8126493.png

Adwaita
https://user-images.githubusercontent.com/45657128/77167630-b0249100-6ab6-11ea-899f-2d7df22f8656.png

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: yaru-theme-gtk 20.04.2
ProcVersionSignature: Ubuntu 5.4.0-18.22-generic 5.4.24
Uname: Linux 5.4.0-18-generic x86_64
ApportVersion: 2.20.11-0ubuntu21
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Mar 21 15:05:30 2020
InstallationDate: Installed on 2020-01-21 (59 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200117)
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: yaru-theme
UpgradeStatus: No upgrade log present (probably fresh install)