(Excuse me if this is the wrong forum for this)
I'm planning on including in my Slaanesh CSM force a mini-warband named the Underminers, a squad or two of Iron Warriors who have defected to the Legion of Vice, both as a homage to the days of old when the Iron Warriors were a Slaanesh-dedicated Legion, and also as an excuse to get to mess about with metallic paint schemes. However, aside from that I'm not entirely sure on the colour scheme for these turncoats. Obviously there will be plenty of metallic paints involved but I have a few different ideas for the specifics:
1: "Scream eternal, noisy and chrome"- Making the metallics very high-shine and bright, as if the need for perfection had lead them to obsessively polish and clean their armour until it was mirror-finished. A good excuse to use some Molotow and other really shiny metallics, and would look quite striking, however as the fluff I've come up with for them has them as subterranean warfare experts who introduced Termites to my Slaaneshi coalition, that might be a bit at odds with them being bright and clean.
2: "Industrial metal"- The opposite end of the spectrum, with their armour being dirtied and worn by ceaseless combat, with their signs of devotion to the Dark Prince including acid-etched patterns, bold insignias and other, less delicate decorations. Would be more appropriate for their fluff but would be potentially difficult to make them obviously Slaaneshi.
3: "High on paint fumes"- A bit of a balance between the two, with extensive use of GSW or Turbodork colour-shift paints for the basic metallics, as these could be weathered whilst still being very, very Slaanesh. Could overly divorce them from the whole Iron Warriors theme though.
Another idea I have is taking the iconic hazard stripes and tweaking them juuuuuust a bit, either choosing different colours or altering the pattern (zigzag/thunderbolt patterns for example).