I think the use of color, and the lack of color, in this image is meant to provoke the idea that the ones who leave have a sense of nostalgia about that wonderful place they left behind.
The woman is in color - which places her in the present. And the rest of the image is in neutral grey tone, which evokes the sense of it being in the past. The KH image, in its muted grey tones, not even any black, is meant to represent the blue lady's memory, her past she left behind.
The little girl on the chair is her - the blue lady as a child. Surrounded by loving family members...inside a Kingdom Hall.
The WT wants the JWs who are still in to believe that those who have left, like the blue lady, look back and miss that idyllic memory.
This is a strong image. The WT uses visual language in a very calculated way.
*pssst...Lol! I am surprised nobody has noticed the demon yet! ;)