Starting from the rightmost input to the p push_grid object, you can see this is wired up to a checkbox. When the checkbox is checked a message goes into the object which essentially says “I’m grabbing you now”. You probably saw the grid switch from the standard Scale display to blank at this point. Live has handed over control of the button grid and we can now use it for our own purposes.
The second checkbox sets a metronome running, which in turn prods the random number generator into producing a number, which is then converted to a text message (the $1 is replaced with the random number) which is sent to the leftmost input, setting a colour on all of the Push’s grid buttons, thus changing the colour at every metronome tick.
Now it’s time to start editing our max4live device... Take a deep breath and click the little plug icon, 3rd from the right of the device’s title bar. This will bring up the max editing window:
I’ve already made a small edit to the device in this screenshot - I’ve double clicked the Message object (directly above p push_grid) and changed the text to read set 0 0 $1. Now lock the device by clicking the small padlock icon at the bottom left. This switches the max4live device into operational mode, and checking the two checkboxes will yield a less dazzling effect than before. We’re now telling the push to only light one button with random colour, in this case the one at 0 0 - the top left. As you’d expect you can change these numbers to anything up to 7 7 (bottom right) which will light different pads in the grid accordingly.
Before - all buttons pulsing, after - top left button pulsing. Congratulations!
From here you can either File - Save As... to keep this edited device for posterity or just close it and play with some of the other example devices. The most interesting of these is 1. Interactive Overview, which contains a good rundown of all the available objects, including a list of all the commands you can use to set colours on the grid and other parts of the Push. (One word of warning - as mentioned in the Kit’s documentation you really should switch the device OFF using Live’s device on/off button - the greenish one at the top left - before removing it from your set, thanks to a slight bug that occurs otherwise.)
I guess I've been trying to recreate a Korg Electribe all this time..