Muslims were identified with darkness as the antithesis of Christ’s light.

Evidence

Darkness was identified with Muslims through the Black Saracen, Islamic islands where the sun was blacked out and all the stones were black, and other images employing darkness—the antithesis to the light of Christ. These are ideas that determined, in part, the history of Christian-Muslim relations. — Sophia Rose Arjana, Muslims in the Western Imagination, 81

Categorization

• SEED: The ‘Black Saracen’ and sun-blackened Islamic islands are concrete visual tropes worth cataloguing as evidence for how color-coding preceded any contact — could anchor an essay on pre-racial color symbolism.
• QUESTION: The ‘Islamic islands where the sun was blacked out’ — where does this image originate geographically and in which texts/authors? Worth chasing the source.