Today (November 3) marks 45 years since Dominica adopted its flag. It is the only national flag using the color purple outside a coat of arms. (El Salvador and Nicaragua have purple in their CoA).

(Since you almost need a magnifying glass to see the small purple fields in the rainbows of the flags of El Salvador and Nicaragua, I think they barely count.)

The original flag from 1978 had the sisserou parrot looking the other direction, and a different color order in the cross:

The current flag dates from 1990 (apparently also adopted November 3).

Wikipedia article about the flag