red ink

Evidence

"Syntax clarification marks are superscript or subscript numerals and/or letters... (e.g. RBD A34, dated 1080/1670). These marks (written often in red) appear here and there in passages in manuscripts and refer to groups of words and show their syntactical relationships. They are encountered mainly in manuscripts from the Ottoman period and penned mostly by non-Arabs."

Remarks

Syntax clarification marks (tadbib) involve the placement of numerals or letters to link related words in a text (p. 258). These are often executed in red ink and are particularly common in Ottoman Turkish manuscripts (p. 259).