If you have the “Display NULL values as (null)” option turned on, you normally see the “(Null)” value in a slight orange color, but if it’s the first column has a null value, it’s displayed as the default font color.
Just execute the following SQL and you will notice
SELECT NULL c1, ‘asd’ c2 FROM DUAL
SELECT ‘asd’ c1, NULL c2 FROM DUAL
select null c1, ‘asd’ c2