What is the safe reading of correspondence between Faʿlala and Istifʿāl?

Final Characteristics of Derived Forms: Ifʿīlāl, Ifʿilāl, Faʿlala, Tafaʿlala, and Related Patterns

• The forms are fully identical
• Every example denotes a color
• Semantic similarity in particular examples
• All four root letters disappear