https://www.hackingwithswift.com/quick-start/swiftui/how-to-read-the-red-green-and-blue-values-from-a-color

ResolvedColorPicker.swift

import SwiftUI

struct ResolvedColorPicker: View {
  @Environment(\.self) var environment
  @Binding private var selection: Color.Resolved
  private let supportsOpacity: Bool
  private let titleKey: LocalizedStringKey

  init(_ titleKey: LocalizedStringKey, selection: Binding<Color.Resolved>, supportsOpacity: Bool = true) {
    _selection = selection
    self.supportsOpacity = supportsOpacity
    self.titleKey = titleKey
  }

  var body: some View {
    ColorPicker(titleKey, selection: .init {
      Color(red: Double($selection.wrappedValue.red),
            green: Double($selection.wrappedValue.green),
            blue: Double($selection.wrappedValue.blue))
    } set: { color in
      selection = color.resolve(in: environment)
    }, supportsOpacity: supportsOpacity)
  }
}

struct ContentView: View {
  @State private var resolvedColor = Color.Resolved(red: 0.0, green: 0.0, blue: 0.0, opacity: 0.0)

  var body: some View {
    VStack {
      ResolvedColorPicker("Select your favorite color", selection: $resolvedColor)

      Text("Red: \(resolvedColor.red)")
      Text("Green: \(resolvedColor.green)")
      Text("Blue: \(resolvedColor.blue)")
      Text("Opacity: \(resolvedColor.opacity)")
    }.padding()
  }
}

#Preview {
  ContentView()
}