Try to use the spannable string to change the text of the menu item. here is the sample code for ur reference.
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.menuId, menu);
SpannableString str = new SpannableString("Menu item text");
str.setSpan(new ForegroundColorSpan(Color.BLUE), 0, str.length(), 0);
menu.getItem(R.id.menuItemId).setTitle(str);
}