The iridescent colour of these beetles is a form of structural colour. The most common form of iridescence in beetles is through multilayer reflection. Imagine a multi-layered cake, sponge layers alternating with cream layers. (If you're still here and not having a snack in the kitchen) Now imagine that each layer is transperant but has a different refractive index. White light falling on our cake will go through each layer, but when it hits a boundary, this light will get split, some will get reflected back upwards. If boundaries are between 380–750 nm apart, ie the wavelengths within the visible light spectrum, the returning light will interfere other relflected light from the top surface. And depending on the depth of each our layers, constructive interference will occur for some visible light wavelength, i.e. some colour will be made super bright within the white light spectrum, and voila presto, structural colour. Here's a nice review on beetle iridescence.
But this picture is about hairiness really, rather than colour. Why are so many insects so hairy? My thought is electrostatics, what's yours?