I am sure my code is correct, since it works in my playground. However I cannot get passed this exercise.

You're not passing for two reasons.

Firstly, when you pass in the parameters for your init method, you shouldn't set the values of the different variables - only the types. While your code should work fine when you set default values to the different parameters, it also creates multiple ways to initialize an RGBColor object, which isn't what the challenge wants you to do. Because of this, the quiz compiler will mark you wrong for that.

Secondly, you need to add the proper spacing in your initialization of self.description. All computers are picky about Strings - if you don't have exactly what the computer expects to find in a String, the computer will freak out. In this case, the fact that you don't have spaces between each colon and interpolated value, as well as after each comma, leads the quiz compiler to mark your answer as false.

The adjustments you need to make are in the code below:

struct RGBColor {
    let red: Double
    let green: Double
    let blue: Double
    let alpha: Double

    let description: String

    // Add your code below
    // REMOVE DEFAULT VALUES FROM DECLARATION OF PARAMETERS
    init(red: Double, green: Double, blue : Double, alpha : Double){
        self.red = red
        self.green = green
        self.blue = blue
        self.alpha = alpha

        // ADD APPROPRIATE SPACING
        self.description = "red: \(red), green: \(green), blue: \(blue), alpha: \(alpha)"

    }
}

I hope this helps!