I pulled out two nail polishes I thought would be similar to Dior Palais Royal (reviewed here), one proved to be a very close match.
Dior Palais Royal and OPI Berlin There Done That are almost exact dupes. OPI is a touch lighter and greyer, but in most light conditions they look exactly the same. Both have great, fast drying formulas.
Illamasqua Stagnate is from a different story – darker, more rich colour, with stronger purple and brown undertones.
From left to right: Illamasqua Stagnate, Dior Palais Royal, OPI Berlin There Done That, Dior Palais Royal
For more comparison swatches check out Sara’s review.