Hi.
I made a Tetris game a few years ago :
http://www.jinxtergames.com/web-games/There i used array maker and several arrays (1 per vertical line)
the reference names of the array i set to 0,1,2,3,etc. this way i can use the position to reference the blocks.
so 0,0 would be top left (array 0 index 0) and 0,23 (array 0 index 23)would be bottom left.
When your block landed you can then get its position and then use Array List Get Next/Previous to check what's next to it.
This part can be a bit intense to setup as you probably want all connected blocks with the same color to be removed.
To check the color you could set a fsm on your block called (for example) Data.
there you can set a int vaule for your 'Color' Id or you could use tags.
i would start by checking horizontal and if the same color blocks are there then add it to an array (connected).
then go thru the connected blocks and check in all directions (but only next to the block not the whole line/row) if a same color exists
Check if the block is already in the list and if not then add to the array (connected)
Then when done you can use Array List Count if you need a certain minimum.
Then you can loop thru the array to despawn then or whatever you need to do with it.