title: How to set a Raised Button's Background Color transparent in Flutter?
body: <p>Here is my code,I'd like to set a background color, transparent to my button.</p>
  
  <p>I'd like to add background color to both Raised Button in my code.
  I also tried wrapping it with a Container and then applying container's background transparent, but it didn't work.</p>
  
  <pre><code>         Column(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: &lt;Widget&gt;[
                  FadeAnimation(
                    3.4,
                    SizedBox(
                      width: double.infinity,
                      height: 44,
                      child: RaisedButton(
                       color: Colors.white,
                        onPressed: navigateToSignUp,
                        child: Text(
                          'Sign Up',
                          style:
                              TextStyle(color: Colors.blueGrey, fontSize: 24),
                        ),
                      ),
                    ),
                  ),
  
                SizedBox(height: 10),
                  FadeAnimation(
                    3.4,
                    SizedBox(
                      width: double.infinity,
                      height: 44,
                      child: RaisedButton(
                        color: Colors.white,
                        onPressed: navigateToSignIn,
                        child: Text(
                          'Sign In',
                          style: TextStyle(color: Colors.grey, fontSize: 24),
                        ),
                      ),
                    ),
                  ),
  </code></pre>