Take the following Python code and refactor it using list comprehensions.
arr = [1, 2, 3, 4, 5, 6] 
new_arr = [] 

for i in arr: 
    if i % 2 == 0: 
        new_arr.append(i**2)
arr = [1, 2, 3, 4, 5, 6] 
new_arr = [i**2 for i in arr if i % 2 == 0]