lot's of led with each there individual switch.

Idea would be as an exemple
4 RGB led arcade button
when you click a button, that button change his own led color
if you press that button again, it goes to the next color.

My questions is pretty simple:
1- is this possible to do ?
2- if possible, how many button can 1 arduino support ?

If this is truly possible, i'll do a giant board with over 150 buttons (will require multiple arduino i am shure)

Thanks for the help guys !

Yes, all possible. Not sure how many buttons an Arduino could support, but probably many times 150. Only one Arduino will be required.

But you will need extra stuff because the Arduino does not have 150 inputs, let alone 450 PWM outputs...

But with that many it's probably a lot easier to split it across like 10 the same devices with all 15 buttons. Otherwise wireing will be a nightmare. A lot more then the code.

Another option could be 150 ATtiny45/85. From what the OP has said, each button/led is independent of the others.

Might be able to use a string of Neopixels for the LEDs.

Leds are easy with addressables. Big number of buttons is the challenge.
I made something like this, just a modern day lite brite busy board.

INTP : that's the thing i am aiming for, a sweet light brite.

The thing is that LED dosen'T come adressable by themself, so an arcade led button woudn't be possible.

Adressable LED strip would clash in the light brite design with the buttons.

There are the shift register controler that could twink the board and make more possibilities.

How did you build yours exactly ?