how to convert gray to color image in cv2 python

i use cv2 python in low-pass-FFt and i already change attribute of image but this image is gray image . i want to change it to color image and keep attribute of gray image

----------
import cv2
import numpy as np
from matplotlib import pyplot as plt


img = cv2.imread('rocket.jpg', 0)
height, width = img.shape

plt.figure("Input")
plt.subplot(221),plt.imshow(img, cmap = 'gray')
plt.title('Input Image'), plt.xticks([]), plt.yticks([])

fft = np.log(np.abs(np.fft.fftshift(np.fft.fft2(img))))
plt.subplot(222),plt.imshow(fft, cmap = 'gray')
plt.title('Fourier Transform'), plt.xticks([]), plt.yticks([])

r = 200
h_Filter_Low_Pass = np.zeros(img.size, img.dtype).reshape(img.shape)
for icounter in range(1, height):
    for jcounter in range(1, width):
        if ((height/2-icounter)**2 + (width/2 - jcounter)**2)**0.5 < r:
            h_Filter_Low_Pass[icounter, jcounter] = 1
plt.subplot(223),plt.imshow(h_Filter_Low_Pass, cmap = 'gray')
plt.title('Filter'), plt.xticks([]), plt.yticks([])

h_fft = (np.abs(np.fft.fftshift(np.fft.fft2(h_Filter_Low_Pass)))+1)
plt.subplot(224),plt.imshow(h_fft, cmap = 'gray')
plt.title('Fourier Transform (Filter)'), plt.xticks([]), plt.yticks([])

fshift = np.fft.fftshift(np.fft.fft2(img))


plt.figure("output")
new = fshift * (h_Filter_Low_Pass)
g_ifft1 = (np.abs(np.fft.ifft2(np.fft.ifftshift(new)).real))



plt.subplot(),plt.imshow(g_ifft1, cmap = 'gray')
plt.title('output'), plt.xticks([]), plt.yticks([])
plt.show()