Setting particular pixel to specified color in the output of segmentation map

Python
2

In case it’s not clear why my first approach to setting pixels to white isn’t working.
this is the result for the first approach
wrong_result

So i tried using the bitwise idea.
Here i converted the image to hsv to get a better understanding of which pixels are set to blue or light blue
The HSV plot is shown below
hsv_ade
from this i think the light blue lower and upper ranges are
(77,90,0) and (125,250,225)
Using this i created the bitwise mask and obtained this beauty
code for masking
bitwise_mask
Code for masking

mask = cv2.inRange(hsv_img, light_b, high_b)
result = cv2.bitwise_and(img, img, mask=mask)
plt.subplot(1, 2, 1)
plt.imshow(mask, cmap="gray")
plt.subplot(1, 2, 2)
plt.imshow(result)
plt.show()

Not sure why the sky is jet black here.

Would appreciate it if some kind soul could help me.Chris i am looking at you as you have always helped me out.