diff --git a/bin/__build_sgr_code b/bin/__build_sgr_code
index a766c26..e38c0de 100755
--- a/bin/__build_sgr_code
+++ b/bin/__build_sgr_code
@@ -162,6 +162,26 @@ function ansi_color()
     fi
 }
 
+function ext_grey()
+{
+    use_8_bit=1
+    grey_val=${1}
+    if (( ${grey_val} < 0 || ${grey_val} > 23 ))
+    then
+        echo "ERROR!" 1>&2 ; exit -1
+    fi
+    ext_8_bit=$(( 232 + ${grey_val} ))
+}
+
+function ext_rgb()
+{
+    use_8_bit=1
+    red_ext_val=$((6#${1:0:1}))
+    green_ext_val=$((6#${1:1:1}))
+    blue_ext_val=$((6#${1:2:1}))
+    ext_8_bit=$(( 16 + 36 * ${red_ext_val} + 6 * ${green_ext_val} + ${blue_ext_val} ))
+}
+
 function ext_color()
 {
     use_8_bit=1
@@ -371,18 +391,24 @@ function build_sgr_code()
         reveal) next=28 ;;
 
         ansi:*) make_color 0 ansi_color ${1:5} ;;
+        ext:grey*) make_color 0 ext_grey ${1:8} ;;
+        ext:rgb*) make_color 0 ext_rgb ${1:7} ;;
         ext:*) make_color 0 ext_color ${1:4} ;;
         # 12-bit color also supported
         [0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) make_color 0 rgb_color $1 ;;
         [0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) make_color 0 rgb_color $1 ;;
 
         fg:ansi:*) make_color 0 ansi_color ${1:8} ;;
+        fg:ext:grey*) make_color 0 ext_grey ${1:11} ;;
+        fg:ext:rgb*) make_color 0 ext_rgb ${1:10} ;;
         fg:ext:*) make_color 0 ext_color ${1:7} ;;
         # 12-bit color also supported
         fg:[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) make_color 0 rgb_color ${1:3} ;;
         fg:[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) make_color 0 rgb_color ${1:3} ;;
 
         bg:ansi:*) make_color 1 ansi_color ${1:8} ;;
+        bg:ext:grey*) make_color 1 ext_grey ${1:11} ;;
+        bg:ext:rgb*) make_color 1 ext_rgb ${1:10} ;;
         bg:ext:*) make_color 1 ext_color ${1:7} ;;
         # 12-bit color also supported
         bg:[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]) make_color 1 rgb_color ${1:3} ;;