How do I create this colorful background

I once did a similar kind of design.

Cut out colored pices of paper and put them on my scanner. The scattered parts of that around in the design.

For yours if you get the arrange right on the scanner, then editing it afterwards migh noch be necessary.

You could scan several different ones, then stack them in Photoshop and add different blurs to them to simulate depth.

It could help to scan them with a color background already in place. Even if you remove that background later when editing, it gives the confetti the correct color along the fringes.

Also put the logo on it, then add some bits in front of it.

As Jacob already alluded, you may use one of the various scripts that can do random distributions of a given selection that consists of different shapes or symbol instances.

Also, Illustrator does offer a couple of ways to randomly distribute things (for example Transform Each, Scatter Brushes or the built-in Symbol tools).

Another funny but useful way would be to buy a packet of confetti (or do the confetti yourself), throw it wildly into the air in front of a single-coloured background and have a good photographer that is able to capture the confetti fireworks. Then you may use that photo as your background. A little bit of luck, and the photographer way may be the most convincing approach.

v,

As I (mis)understand it, you wish to have what is more or less termed a spray of (more or less) random symbols/shapes.

It can take a lot of time to make such a mess, but I believe there are scripts to easily spray random symbols from a larger set.