--- /dev/null
+diff --git a/Makefile b/Makefile
+index 3315fb5..eb211c4 100644
+--- a/Makefile
++++ b/Makefile
+@@ -1,6 +1,6 @@
+-INSTALL_DIR=/usr/local/bin
+-MAN_DIR=/usr/local/man/man1
+-ETC_DIR=/etc
++INSTALL_DIR?=/usr/local/bin
++MAN_DIR?=/usr/local/man/man1
++ETC_DIR?=/etc
+ VERSION=$(shell egrep '^my .version' colordiff.pl |cut -f 2 -d "'")
+ DIST_FILES=COPYING INSTALL Makefile README \
+ colordiff.pl colordiffrc colordiffrc-lightbg cdiff.sh BUGS CHANGES colordiff.1 \