How to make game like that ?

Hello guys,
I want to make a game like this. When ball throw it will change color with an effect. And drop balls at end of level. How can i make an effect like this ?

Best Regards

 

Have each sphere track its neighbours. When the incoming projectile collides with a sphere, use a flood fill algorithm to recursively change the colours of itself and each neighbour as long as they match colours.

https://en.wikipedia.org/wiki/Flood_fill