Unable to change default fill and border colors of hierarchical sheets

Description

There is no mechanism to change the fill color of hierarchical sheets in Preferences > Eeschema > Colors

Hierarchical sheets are now filled white, which is sub-optimal when using a dark background color in Eeschema.

KiCad Version

Application: Eeschema
Version: (5.99.0-1233-g710e93bc5), release build
Libraries:
    wxWidgets 3.0.4
    libcurl/7.69.1 OpenSSL/1.1.1e zlib/1.2.11 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh2/1.9.0 nghttp2/1.40.0
Platform: Linux 5.4.28-1-MANJARO x86_64, 64 bit, Little endian, wxGTK
Build Info:
    Build date: Apr  6 2020 09:58:56
    wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
    Boost: 1.72.0
    OpenCASCADE Technology: 7.4.0
    Curl: 7.69.1
    Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_PYTHON3=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
    KICAD_SCRIPTING_ACTION_MENU=ON
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=OFF
    KICAD_USE_OCC=ON
    KICAD_SPICE=ON