Creating Instance Of Circle With A Diameter Of 50 And Green Colour

I have two classes LightController & Circle. I need to use the LightController class to do the following:

Creates an instance of Circle with a diameter of 50 and a colour of OUColour.GREEN and assigns this new circle to the instance variable light.

Sets the xPos of light to 122.
Sets the yPos of light to 162.

I am struggling to write the correct line of code to set the colour to green and set diameter to 50.

Code for the two classes below.

import ou.*;
import java.util.*;
/**
* Class LightController
* This class uses the Circle class, and the Shapes window to simulate a disco light, that grows and shrinks and changes colour.
*/

public class LightController
{
/* instance variables */
private Circle light; // simulates a circular disco light in the Shapes window
private Random randomNumberGenerator;

[Code] ....