Got home to realise youve bought a polish you already have? Grab your old polish and add a dash of white to give yourself a lighter shade! Or if you're feeling brave, add a different colour to it and mix to create a custom colour!
I did just that with a peach melba from Barry M which I already owned, and silly me bought another thinking I didn't have it, so I added some bright red and created a lovely pink! (Middle in picture)