Android(Canvas)-ทำยังไงให้วงกลมเปลี่ยนสีตามเงื่อนไขคะ

package com.example.tutor;


import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.LinearLayout;


public class Draw extends Activity{
	 TextView edtinput;
	 static String msg;
	 static String input;
	 
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
	    setContentView(R.layout.activity_draw);

	    Bundle bundle = getIntent().getExtras();
		  msg = bundle.getString("Message");
          edtinput = (TextView)findViewById(R.id.textView1);
		 edtinput.setText(msg);
 
LinearLayout show = ( LinearLayout)findViewById(R.id.linlay);
		
		graph graph = new graph(this);
	
		show.addView(graph);
	}
	
	static public class graph extends View {
		Paint paint1;
		Paint paint2;
		Paint paint3;
	

		public graph(Context context) {
			super(context);
	
			
		}
		protected void onDraw(Canvas canvas){

   		 
   	       if(msg=="blue"){
   			paint1 = new Paint();
   			paint1.setColor(Color.BLUE);
   		    paint1.setStyle(Paint.Style.FILL);
   		    
   		    canvas.drawCircle(85, 80, 35, paint1); 
   		  
   	}
   	 
   	else if(msg == "green"){
   		  paint2 = new Paint();
   		  paint2.setColor(Color.GREEN);
		  paint2.setStyle(Paint.Style.FILL);
   		  
   		   canvas.drawCircle(85, 80, 35, paint2);
   		  
   	}else{
   		  paint3 = new Paint();
 		  paint3.setColor(Color.GRAY);
		  paint3.setStyle(Paint.Style.FILL);
 		  
 		   canvas.drawCircle(85, 80, 35, paint3);
   		
   		
   		
   		
   	}
 	    

	}}}