The Iridescent texture node produces an effect where surfaces appear to gradually change color as the angle and illumination of view changes (figure 1).
Figure 1: The Iridescent node applied to a scene object
Figure 2: The Iridescent node and it's associated parameters
Base Color
Determines the base color underlying the other iridescent colors.
Primary Color
The first color layer above the base color.
Secondary Color
Provides an additional color layer to mix with the base and primary colors.
Tertiary Color
Provides an additional color layer to mix with the secondary, primary, and base colors.
Thickness Map
Determines the thickness of the color bands.
Thickness Scale
A scale value applied to the thickness map.
Iridescent Exponent
Adjusts the overall shape of the iridescent effect.
Frequency
Determines how many color bands are generated.
Noise Frequency
Adjusts the smoothness of the color bands.
Noise Scale
Determines the scale of the noise parameter.
Period Offset
Adjusts the positioning of the color bands across the surface.
Iridescence Weight
Blend the primary, secondary, and tertiary color bands with the base color.
Transform
Positions, scales, and rotates the surface texture.
Projection
Sets how the texture projects onto the surface.