Q:

Change calendar button color for showDatePicker

I'm using showDatePicker to display a calendar.  How do I change the button color and also the today's date background color

I've tried different colors setting in Theme Data.  but the OK, Cancel & today's date still in blue
Theme(data: ThemeData(
      splashColor: Color(0xFFFE9BC0),
    )
    child: myWidget(),
);

A:

What i did to change the color of the datePicker was:
Theme(
  data: ThemeData(primarySwatch: Colors.red),
  child: myWidget(),
);

Setting an appropriate primarySwatch instead of splashColor will change all the appearance of the picker, this is because a swatch is like a palette of color. 
Another thing you could do is set a primarySwatch with a MaterialColor similar to the one you want as main color and then customize the splash color or primary color like this:
Theme(
  data: ThemeData(primarySwatch: Colors.red, splashColor: Colors.green),
  child: myWidget(),
);

Hope it helps!