how can ı make multiple blasting ?

I want to make like this game but ı need to find best way for multiple detect color.

 

Every barrel in the setup have 6 ajanced barrel. Save neighbor list for every barrel and check all neighbors colors if match.

 

Should ı use a array or collision detect ? for neighbor

 

Array. Use collision detection when environment have a lot of variations or totally unknown. Here's your scene contains only barrels on top each other in precalculated positions so you can easily fill in all neighbors array while generating or loading the level.