I have made myself a numpy array from a picture using

```
from PIL import Image
import numpy as np

image = Image.open(file)
np.array(image)

```

its shape is `(6000, 6000, 4)` and in that array I would like to replace pixel values by one number lets say this green pixel `[99,214,104,255]` will be `1`.
I have only 4 such pixels I want to replace with a number and all other pixels will be `0`. Is there a fast and efficient way to do so and what is the best way to minimize the size of the data. Is it better to save it as `dict()`, where keys will be `x,y` and values, will be `integers`? Or is it better to save the whole array as it is with the shape it has? I only need the color values the rest is not important for me. 

I need to process such a picture as fast as possible because there is one picture every 5 minutes and lets say i would like to store 1 year of data. That is why I'd like to make it as efficient as possible time and space-wise.