### Add graphs produced by a for loop?

How can I plot all my graphs that i produce from a for loop on top of each other? I have this:

for i in range(-3,3,1):
p1 = parametric_plot((t,i),(t,-5,5),color="red")
p2 = parametric_plot((i,t),(t,-5,5),color="gray")
show(p1+p2)

I just get all the graphs one after the other.