The gist updates the color of the progress bar every few seconds like Inbox by Gmail app. The detailed explanation can be found in my blog post http://gsrikar.blogspot.com/2017/01/how-to-update-circular-progressbar.html

Update Progress Bar Color Continously

/**
 * The amount of time that has to pass to update the progress bar color
 */
private static final long UPDATE_TIME_IN_MILLIS = 2000;

/**
 * List of all the desired colors of the progress bar
 */
private ColorStateList[] colorsList;

/**
 * Variable is used to choose a color from the colorsList array
 */
private int position = 0;

// UI element
private ProgressBar progressBar;

// Handler
private Handler updateProgressColorHandler;

// Runnable
private Runnable updateProgressColorRunnable;

/**
 * Update the color of the progress bar every few seconds
 */
private void showAndUpdateProgressColor() {
    // Initialize the color list
    colorsList = new ColorStateList[]{
                ColorStateList.valueOf(Color.BLUE), ColorStateList.valueOf(Color.RED),
                ColorStateList.valueOf(ContextCompat.getColor(this, R.color.color_yellow)),
                ColorStateList.valueOf(Color.GREEN),
                ColorStateList.valueOf(Color.MAGENTA), ColorStateList.valueOf(Color.CYAN)};
    // Initialize Runnable
    updateProgressColorRunnable = new Runnable() {
        @Override
        public void run() {
            Log.i(TAG, "Position: " + position);
            Log.i(TAG, "Colors List Length: " + colorsList.length);
            if (position >= colorsList.length) {
                // There are no more elements in the array
                // Reset the position
                position = 0;
                Log.i(TAG, "Position is set to zero");
            }
            // Change the progress bar color
            progressBar.setIndeterminateTintList(colorsList[position]);
            // Increment the position
            position++;
            Log.i(TAG, "Updated Position: " + position);
            // Call the runnable again with a delay
            updateProgressColorHandler.postDelayed(updateProgressColorRunnable, UPDATE_TIME_IN_MILLIS);
        }
    };

    // Initialize Handler
    updateProgressColorHandler = new Handler();
    // Use the handler to add the runnable to the message queue
    updateProgressColorHandler.post(updateProgressColorRunnable);
}