Coding Probability in Swift

I want to write a program that creates say 100 squares, with the following rules:

up to - but no more than 10% of them will be blue
up to - but no more than 15% of them will be red
up to - but no more than 25% of them will be yellow
and the rest of them will be orange

So basically every time I run the App I'll get totally different results. For example, the first time I might get:

9 blues
13 reds
18 yellows
and 60 oranges

The next time I might get:

6 blues
14 reds
23 yellows
and 57 oranges

And so on.

I tried doing this using random numbers but every single time I get the absolute max # from each color category - I basically never had any classes in Probability (or Statistics) so I really have no idea what I'm doing here - thought maybe someone could point me in the right direction or knows how to do Probability in Swift code...?

Solution

This function will return an array of 100 randomized UIColors matching your probability requirement. This code includes a probability of zero for each of the three main colors. If you want to include a probability of at least one of each color then change the range to 1...n

func generateRandomColors() -> [UIColor] {

    var randomColors = [UIColor]()

    randomColors += Array(repeating: .blue, count: .random(in: 0...10))
    randomColors += Array(repeating: .red, count: .random(in: 0...15))
    randomColors += Array(repeating: .yellow, count: .random(in: 0...25))
    randomColors += Array(repeating: .orange, count: 100 - randomColors.count)

    return randomColors.shuffled()
}