To Change the Text color :
int searchSrcTextId = getResources().getIdentifier("android:id/search_src_text", null, null);
EditText searchEditText = (EditText) searchView.findViewById(searchSrcTextId);
searchEditText.setTextColor(Color.WHITE);
searchEditText.setHintTextColor(Color.LTGRAY);
To Change the close button :
int closeButtonId = getResources().getIdentifier("android:id/search_close_btn", null, null);
ImageView closeButtonImage = (ImageView) searchView.findViewById(closeButtonId);
closeButtonImage.setImageResource(R.drawable.ic_action_cancel);
// This excerpt is from Android source code (SearchView.java)
mSearchButton = findViewById(R.id.search_button);
mSearchEditFrame = findViewById(R.id.search_edit_frame);
mSearchPlate = findViewById(R.id.search_plate);
mSubmitArea = findViewById(R.id.submit_area);
mSubmitButton = findViewById(R.id.search_go_btn);
mCloseButton = (ImageView) findViewById(R.id.search_close_btn);
mVoiceButton = findViewById(R.id.search_voice_btn);
mSearchHintIcon = (ImageView) findViewById(R.id.search_mag_icon);
Reference : link