Holographic iridescence is the oil-slick foil look: a thin laminate that splits incoming light into angle-shifting cyan→pink→purple bands, laid over a near-black substrate the way oil spilled on black cement reads as rainbow shimmer.

Born of packaging, brand foiling, and internet-native gradient culture peaking around 2021, the signature is not the rainbow alone but the rainbow anchored against deep dark so the shimmer keeps its depth. It says future-luxe, synthetic, light-as-material.