Changing the GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" option in the /etc/default/grub file into GRUB_CMDLINE_LINUX_DEFAULT="nomodeset acpi_backlight=vendor" seems to bring back the proper colors to the monitor.
Changing the GRUB_CMDLINE_ LINUX_DEFAULT= "quiet splash" option in the /etc/default/grub file into LINUX_DEFAULT= "nomodeset acpi_backlight= vendor"
GRUB_CMDLINE_
seems to bring back the proper colors to the monitor.