Bug#714414: 05_debian_theme: make colours user-configurable

[Martin-Éric Racine]

Package: grub-pc
Version: 2.02~beta3-5
Followup-For: Bug #714414

This issue is caused by hardwired colors in 05_debian_theme.

Unless the script finds that 1) GRUB is running on an Ubuntu host OR that 2) a background image exists, cyan/blue and white/blue colors are enforced.

Adding insult to injury, /etc/default/grub does not offer any means of overriding this.

IMHO, the best solution would be to stop enforcing any default color scheme whatsoever.

-- System Information:
Debian Release: 9.0
  APT prefers stable
  APT policy: (500, 'stable'), (500, 'oldstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/8 CPU cores)
Locale: LANG=fi_FI.utf8, LC_CTYPE=fi_FI.utf8 (charmap=UTF-8), LANGUAGE=fi_FI.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages grub-pc depends on:
ii  debconf [debconf-2.0]  1.5.61
ii  dpkg                   1.18.24
ii  grub-common            2.02~beta3-5
ii  grub-pc-bin            2.02~beta3-5
ii  grub2-common           2.02~beta3-5
ii  ucf                    3.0036

grub-pc recommends no packages.

grub-pc suggests no packages.

-- debconf information excluded