Euro­zone par­tic­i­pa­tion (Wikipedia). BLUE: 19 EU mem­bers in the Euro­zone. YELLOW: EU mem­bers oblig­ed to join the Euro­zone (Bul­gar­ia, Croa­t­ia, Czech Repub­lic, Hun­gary, Poland, Roma­nia and Swe­den). PINK: EU mem­ber with euro opt-out (Den­mark). RED: EU mem­ber vot­ing to leave (UK). GREEN: Non-EU mini-states using euro with a mon­e­tary agree­ment (Andor­ra, Mona­co, San Mari­no, Vat­i­can City). PURPLE: Non-EU states using the euro uni­lat­er­al­ly (Koso­vo, Montenegro).