TheNiels17 has made a fantastic automated warehouse system.
There are 9 bays, each identified by a 3x3 matrix. Each is identified by a 2 colour combination, so Blue:Green is row 1:column 2, Yellow:Green is row 3, column 2 etc
By assembling a little 'swipe' card with the various colours,you can tell the robot what space you are referring to. You can also tell the robot if it needs to place the 'palette' (white code) or pick the palette (black) code.
So a Green:White:Yellow swipe means - Place the palette at location 2:3
and a Yellow:Black:Blue swipe means - Pick the palette from location 3:1
Of course he's implemented error checking so you can place a palette in an occupied space and you pick a palette if there is nothing there in the first place. Just totop it all off, there is a random function to place a palette in a random, unoccupied spot.
If this didn't make sense, watch the video, it does a far better job of demonstrating it than my description :)