This can be achieved using a Spannable String. You will need to import the following
import android.text.SpannableString;
import android.text.style.BackgroundColorSpan;
import android.text.style.StyleSpan;
And then you can change the background of the text using something like the following:
TextView text = (TextView) findViewById(R.id.text_login);
text.setText("");
text.append("Add all your funky text in here");
Spannable sText = (Spannable) text.getText();
sText.setSpan(new BackgroundColorSpan(Color.RED), 1, 4, 0);
Where this will highlight the charecters at pos 1 - 4 with a red color. Hope this helps!