diff --git a/djvureader.lua b/djvureader.lua
index 034b58c3d..129a4e2ba 100644
--- a/djvureader.lua
+++ b/djvureader.lua
@@ -21,8 +21,25 @@ end
 function DJVUReader:adjustDjvuReaderCommand()
 	self.commands:del(KEY_J, MOD_SHIFT, "J")
 	self.commands:del(KEY_K, MOD_SHIFT, "K")
+	self.commands:add(KEY_R, nil, "R",
+		"toggle rendering mode: b&w/colour",
+		function(DJVUReader)
+			DJVUReader:toggle_render_mode()
+		end)
 end
 
+-------------------------------------------------------
+-- toggle rendering mode between colour (0) and b&w (1)
+-------------------------------------------------------
+
+function DJVUReader:toggle_render_mode()
+	InfoMessage:show("New render_mode = "..self.render_mode, 1)
+	Debug("toggle_render_mode, render_mode=", self.render_mode)
+	self.render_mode = 1 - self.render_mode
+	self:clearCache()
+	self.doc:cleanCache()
+	self:redrawCurrentPage()
+end
 
 ----------------------------------------------------
 -- highlight support 
@@ -41,4 +58,3 @@ function DJVUReader:invertTextYAxel(pageno, text_table)
 	end
 	return text_table
 end
-