

The latter two could be considered more "iridescent" than "duochrome" but they are still pretty imo. Violet Voss also has a Sugar Crystals palette that has some duochromey shades as well along with rainbow mattes.

For a very basic starting kit Sephora is selling the 4-color KVD Alchemist palette on sale for $10 currently and it comes with shades in pinky-peach, purple, blue and green which give you lots of options if you layer them over other basic shadows. There may be more and are like $21 each) and in their Moondust line (Solstice is a very pretty sort of teal with a pinky-maroon shift, but they are like $23/each). Other options are Urban Decay has a couple duos in their shadow line (I think one is called Fireball and is peachy-pink and Lounge is a brick red with green duo. You could possibly track some down on poshmark or something too. To me any shimmery burgundy colour is one and done too.
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Any of Charlotte Tilbury cream eyeshadows in pots. I just looked on their site and while the shadows are discontinued, they do still have some of the loose pigments on sale for $6 each. My favorite one and done is CP Glass Bull (its a single) - such a beautiful color MAC Tan pigment, MAC Woodwinked eyeshadow, MAC Groundwork paint pot. I bought the Makeup Geek duochrome set a while back that came with the pressed shadows and the pigments and I love them.
