Do you have to find a pretext to have an iridescent dinner party ?
If you translate this question in to party language, the question is: if the decor is iridescent do you need to do a party or dinner with a mermiad, dolphin or Seapunk theme ? No, it's not obligatory, it's possible to just use the color without explanation. It's during this type of party that you recognise who your real friends are ! Because an iridescent party looks like a shiny gift. And the gift reflects all the colors around you so if you want to keep a touch of iridescent light, advise your friends to dress in pastel colors !
How do you do iridescent decor ?
Just go for foil (curtains or balloons), iridescent tableware (there are some in all shades), iridescent confetti or confetti launchers and you're done !