The noun (Substantiv/Nomen) Grüne is feminine in German. Therefore, the correct definite article in the nominative singular is die. So, you say: die Grüne.
(Greens)
Eine politische Partei, die sich für Umweltschutz und soziale Gerechtigkeit einsetzt.
A political party that advocates for environmental protection and social justice.
Die Grünen sind im Parlament vertreten.
The Greens are represented in parliament.
The noun (Substantiv/Nomen) Grüne is feminine in German. Therefore, the correct definite article in the nominative singular is die. So, you say: die Grüne.
(greens)
Gemüse.
Green vegetables.
Ich esse gern Grüne.
I like to eat greens.