Calling onDraw() method of a custom View in Android

I have created a CustomView for Calendar. I have an onDraw method to draw the text in the calendar. I want to change the color of the day Text when i click on it. How can i achieve it?

CalendarView.java :

package com.example.calendar_module;

import java.util.Calendar;

import android.app.ActionBar.LayoutParams;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.MonthDisplayHelper;
import android.view.MotionEvent;
import android.widget.ImageView;

public class CalendarView extends ImageView {

private static int WEEK_TOP_MARGIN = 0;
private static int WEEK_LEFT_MARGIN = 05;
private static int CELL_WIDTH = 20;
private static int CELL_HEIGH = 20;
private static int CELL_MARGIN_TOP = 05;
private static int CELL_MARGIN_LEFT = 29;
private static float CELL_TEXT_SIZE;
private static int CALENDAR_WIDTH;
private static int CALENDAR_HEIGHT;

private static final String TAG = "CalendarView"; 
private String[] mDayString = {"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
private Calendar mRightNow = null;
private Drawable mWeekTitle = null;
private Cell mToday = null;
private Cell[][] mCells = new Cell[6][7];
private Cell[] mDayCells = new Cell[7];
private OnCellTouchListener mOnCellTouchListener = null;
MonthDisplayHelper mHelper;
Drawable mDecoration = null;

public interface OnCellTouchListener {
    public void onTouch(Cell cell);
}

public CalendarView(Context context) {
    this(context, null);
}

public CalendarView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public CalendarView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mDecoration = context.getResources().getDrawable(R.drawable.typeb_calendar_today);      
    initCalendarView();
}

private void initCalendarView()