If one LED in a row goes open then just make more rows. With enough LEDs the loss of light from a small number will not even be noticed. If four blades of grass in your lawn go brown while the rest stay green then I can be sure that you do not notice those that went brown. The same applies here as long as you take care to provide for a big enough number of LEDs. That may also be the argument why it may be beneficial to use green LEDs.

Michael Karas