title: swift 3 convert string color to cgcolor
body: <p>I am new on swift and iOS and there is something I don't know what should I do.</p>
  
  <p>I have colors coming from backend and I want to convert it to <code>CGColor</code></p>
  
  <pre><code>"colors": [
          "6909A1",
          "7552D1",
          "59B0DC",
          "62E3CC"
        ],
  
  func drawGradient(colors: [CGColor]) {
          addLayer(colors: colors)
      }
  </code></pre>
  
  <p>What should I do here to pass <code>CGColor</code> array after converting it from JSON.
  I couldn't find the right solution how to get <code>CGColor</code> from simple String</p>