python function to change RGB values of an image

Question

I have this function that solely displays the red RGB values of an image. However, I am confused about how the function works. Specifically, why is there a 0 in brackets in this line:

newimage[i][j] = [image[i][j][0], 0, 0]

How can I alter this function to swap the green and blue RGB values while keeping the red value the same?

from matplotlib.pyplot import imshow #command to display a 2D array as an image
from imageio import imread #command to read images from a file or url

coffee = imread('imageio:coffee.png') #Image

def RedImage(image):
    newimage = ArrayOfZeros(400, 600)
    for i in range(400):
        for j in range(600):
            newimage[i][j] = [image[i][j][0], 0, 0]
    return newimage

imshow(RedImage(coffee))