标准化色标，persp()图在面板中，R

I'm creating a panel with multiple persp plots, each showing a range of data generated by tweaking predictor variables in a complex regression model. I want my 3D surface to be color coded by my z variable, which I was able to do easily enough. How do I take this color scale and make it cover the range of all z variable values that would be represented by all plots in my panel, so that the color scale between multiple persp plots can be compared? I'm creating a panel with multiple persp plots,