Question
I live in the Albuquerque area, and in my previous home i had a raywood ash that turned Purple-red way before any other tree.  I have a new home and tree now which is still green eventhough others in the area are already purple-red.  the landscaper says he asked an expert who said becuse our tree looks very healthy and well watered it will take more time to turn it's fall color.  the tree was planted in the spring and is large, about 15' now and the temperature has been dipping down to the low 50s at night

Answer
I would not worry about this tree if it looks healthy. The color will come--some trees turn at different times then others--- could be the amount of water or just the genetic makeup of the tree. In any case sounds like you have done the right things with this tree and it seems healthy.