Auch wenn ich so mach:

SELECT '<span style="' ||
CASE WHEN (0 - Bestand.delta) < 0 THEN
'color:red;">' || (0 - Bestand.delta)
ELSE
';">' || (0 - Bestand.delta)
END || '</span>' (0 - Bestand.delta)
FROM Bestand

kommt der gleiche fehler:

Query cannot be parsed within the Builder. If you believe your query is syntactically correct, check the ''generic columns'' checkbox below the region source to proceed without parsing. ORA-00923: FROM keyword not found where expected