just put a timer on the form and set its interval to 1000 that is, representing milliseconds... .

play Button:
Code:
Timer1.start();
Now on ur .cs file...

Code:
public int a=10;
then on the timer's tick event.put the following code
Code:
a--;
if(a==10)
  this.backcolor= color.red;

else if(a==9)
  this.backcolor= color.blue;
and so on....