grub theme

default/grub:
+GRUB_VIDEO_BACKEND="vbe"
+GRUB_TERMINAL_OUTPUT="gfxterm"
+GRUB_THEME="/boot/grub/themes/custom/theme.txt"
+GRUB_GFXMODE=800x600

theme.txt:
title-text: ""
desktop-color: "#000000"
terminal-left: "0"
terminal-top: "0"
terminal-width: "100%"
terminal-height: "100%"
terminal-border: "0"

+ boot_menu {
  left = 20%
  top = 30%
  width = 70%
  height = 60%
  item_color = "#6d6d6d"
  selected_item_color = "#ffffff"
  icon_width = 32
  icon_height = 32
  item_icon_space = 20
  item_height = 36
  item_padding = 5
  item_spacing = 15
}

+ progress_bar {
        left = 50%-100
        top = 10%-10
        width = 200
        height = 20
        id = "__timeout__"
        text = "@TIMEOUT_NOTIFICATION_SHORT@"
        text_color = "#ffffff"
        border_color = "#6d6d6d"
        bg_color = "#000000"
        fg_color = "#6d6d6d"
}