How to change the function plot colour in Grapher and make it persistent?

Here's y=x^2 plotted in blue: I coloured the function by going to "Window > Show Inspector". So all is nice and smooth, but when I change the function to, say, y=x^3, the plot turns black and has an the width of 1.0 again: How to keep the style of the function object the same, even if I change its parameters?