title: What color system does flutter use and why do we use `const Color` instead of `new Color`
body: <p>Today I came over following snippet of code that implements gradient in flutter</p>
  
  <pre><code>return new Container(
    ...
    decoration: new BoxDecoration(
      gradient: new LinearGradient(
        colors: [
          const Color(0xFF3366FF), 
          const Color(0xFF00CCFF),
        ]
        begin: const FractionalOffset(0.0, 0.0),
        end: const FractionalOffset(1.0, 0.0),
        stops: [0.0, 1.0],
        tileMode: TileMode.clamp
      ),
    ),
  ),
  </code></pre>
  
  <p>And it raised 2 questions:</p>
  
  <p>1) What color system is <code>0xFF3366FF</code> this? it looks somewhat similar to HEX, but it isn't.</p>
  
  <p>2) Why do we use <code>const</code> for <code>const Color()</code> opposed to <code>new Color()</code> I understand different between both, but const here feels unintuitive for me, I'd expect it to be creating a <code>new Color()</code> class instance, similarly to how we use <code>new Text("Some text")</code>. If it needs to be const, why isn't <code>TileMode.clamp</code> also a const?</p>