"column ... does not exist" error when calling an SQL procedure (new in PostgreSQL 11)
The problem is with the parameter assignment in the call. To fix:
CALL config.sp_add_holiday(holiday_date =&gt; '2018-01-01', name =&gt; 'New Years Day');

db&lt;&gt;fiddle here
Explanation
Parameter notation is the same for functions and procedures (new in Postgres 11). The manual:

See Section 4.3 for the full details on function and procedure call syntax, including use of named parameters.

Bold emphasis mine.
You have been using = by mistake. That's the plain old &quot;equal&quot; operator, forming a boolean expression. Obviously not what you intended. The expression is evaluated, Postgres looks for a column named &quot;holiday_date&quot; in the calling SQL context and cannot find it. Hence the error message:

ERROR: column &quot;holiday_date&quot; does not exist


Only =&gt; (SQL-standard notation ) or := are valid for parameter assignment in the call. Details in the manual. Related:

Functions with variable number of input parameters

There is a history of misunderstandings around the use of ...

... the operators = and := in plpgsql code.
... the use of = as short syntax for DEFAULT in CREATE FUNCTION and now also CREATE PROCEDURE statements.
... the assignment notation =&gt; and := in function calls.

Further reading:

The forgotten assignment operator “=” and the commonplace “:=”