Possibly you add a callback in the same method in which you are setting the new color to your text view.

Example

public void setNewTextColor(int color) {
   yourTextView.setTextColor(color);
   yourCallbackMethod();
}

public void yourCallbackMethod() {
   //you can do whatever in this method
}

Update –
You can add your custom textview and define your callback by overriding the setTextColor method inside your custom textview class.

Official guide to create a custom view in android – https://developer.android.com/training/custom-views/create-view

AFAIK, there is no documented, official way to achieve what you want.
But I may suggest a workaround for this, although it’s some kind of overkill. I vouch for this answer for flexibility since it can fit for almost any use cases that involved with TextView usage.

You can create a custom TextView by extending TextView class, and add a custom interface in your custom TextView class that can be used to apply a color change listener. Like this:

public class MyCustomTextView extends TextView {
   // other code, but you not need it since it's already inherited from the parent; unless you want to customize them too.

   public interface OnColorChangeListener {
        void onColorChanged()
   }

   private OnColorChangeListener onColorChangeListener;

   // a public method to apply a color change listener interface to your TextView
   public void setOnColorChangeListener(OnColorChangeListener onColorChangeListener) {
       this.onColorChangeListener = onColorChangeListener;
   }

   public void setTextColor() {
      // REMEMBER & BE AWARE: this is the original TextView method for setting a color.
      // here you can call the listener onColorChanged() method.
      onColorChangeListener.onColorChanged()
   }
}

The next step for you is to change your TextView within the XML layout file to this custom TextView class. Then, in your activity/fragment where you want to listen for color changes, you can do it simply like this:

yourCustomTextView.setOnColorChangeListener(new MyCustomTextView.OnColorChangeListener() {
      void onColorChanged() {
            Toast.makeText(context, "Your text", Toast.LENGTH_SHORT).show();
      }
});

With approach like this, every time you change the color of your custom TextView the toast will be shown.

Hope this helps. Feel free to comment if you do not understand/want to suggest.
Happy coding!

For example I would like to print a Toast –>COLOR CHANGED<– every time I change the textColor of TextView programmatically. Is this possible?