make buildtest output coloured

Makefile.include

@@ -104,5 +104,5 @@ debug:
 buildtest:
 	@for BOARD in $$(find $(RIOTBOARD) -mindepth 1 -maxdepth 1 -type d \! -name \*-common -printf '%f\n' ); do \
 		echo -n "Building for $${BOARD} .. "; \
-		env -i HOME=$${HOME} PATH=$${PATH} BOARD=$${BOARD} RIOTBASE=$${RIOTBASE} RIOTBOARD=$${RIOTBOARD} RIOTCPU=$${RIOTCPU} $(MAKE) -B clean all >/dev/null 2>&1 && echo "success" || echo "failed"  ; \
+		env -i HOME=$${HOME} PATH=$${PATH} BOARD=$${BOARD} RIOTBASE=$${RIOTBASE} RIOTBOARD=$${RIOTBOARD} RIOTCPU=$${RIOTCPU} $(MAKE) -B clean all >/dev/null 2>&1 && echo -e "\033[1;32msuccess\033[0m" || echo -e "\033[1;31mfailed\033[0m" ; \
 	done