Let us make some changes to the function and change the color of the plot.
The Functions sidebar lists all the functions that you have plotted. If y = x^2 isn't already selected, select it. Here you have access to a lot of options. Let us rename the function and move the plot 5 units down. Change the function equation to
parabola(x) = x^2 - 5
and hit enter. To select another color for the plot, click the Color button in the section Appearance at the bottom of the function sidebar and select a new color.
All changes can be undone via → .