How Often Should You Change Power Steering Fluid

What is your question?

I have been told by two garage mechanics that my power steering fluid should be change and flushed. I am told the fluid has a dark color and should be changed. I have looked at the power steering well and the color of the fluid looks pink color to me. I have only had to add fluid once since I bought the car in 2004. Should I have the fluid changed at different maintenace intervals or wait until I have to have the system repaired.