Iridescence on rendering can be quite useful for creating a wide range of effects. Iridescence can be used on anything from bubbles, insect shells, pearlescent ceramic and car materials, to holographic effects.
Redshift has a couple of shaders that can handle these type of effects in both the rsCarPaint and rsMaterial shaders. Watch Concept Artist and Matte Painter, Saul Espinosa who covers creating Iridescence and thin film effects by working through a specialized car paint, and bubble material. Saul also goes into using the Maya samplerInfo node along with rsFresnel (which works similarly) to control how colors are being introduced into the shader attributes.
Saul has been publishing a lot of tutorials getting users oriented with the extremely fast Redshift GPU based renderer. Check out the rest of the tutorial series here.