this one is more like poly-pencil-scape.
source image: colorful pencils

Did you desaturate the image after selection, Tin? It's very nice the effect.

Thanks,
Nope, I don't touch the original background image.
I add a layer fill it with black (or white as long as it's a color that has RGB of the same value), then add layer mask of white, set mode to color, then paint mask with black where i want to reveal color.
The 2 circles are just gradient added on another layer.

Thank you Tin. Another effect for me to try.