I thought the Renes had the square partridge style sights?
But as long as you are going to switch them out you might want to do what I did with my Hawken sights. Again the white fingernail polish. (I have to keep using it ever since my wife found it in my truck!)
On the rear sight I mask an inverted triangle (point up) right to the center of the "U" and then I paint the front sight with the white polish. Works great even in low light.
Hint, Don't make the triangle too wide on the bottom. Maybe only about 1/16".