"A green-white dress"

Translation: Ein grün-weißes Kleid

[MusicMan82]

Do other hyphenated adjective pairs behave this way too?

[Menschenkind]

What exactly do you mean? Which behaviour precisely? Hyphenated adjectives aren't very common, but a rule is: the first word is used in nominative, while the second one gets inflected.

[MusicMan82]

Thanks! That's exactly what I mean.

[kmramna]

Danke dir!

[Adawg12040]

Why isn't "grün" "grünes"?

[pada.online]

The compound grün-weiß constitutes a single adjective. The suffix -es is only appended once to the end of the adjective.

[philster043]

I entered "Ein grünweißes Kleid" and it was accepted, albeit it "corrected" me for leaving out the "-" and called it a typo. My German friend would type it without the "-" though, dunno if it's the spelling reform or what.

[pada.online]

The hyphen is used to emphasize the border between coequal words like "green" and "white". So it is better to add the hyphen in this case.

[arghand]

Why "weißes" and not only "weiß"?

[pada.online]

The suffix -es of adjective weiß tells that the noun das Kleid is neuter.

• der weiße Tisch - ein weißer Tisch (male)
• die weiße Lampe - eine weiße Lampe (female)
• das weiße Kleid - ein weißes Kleid (neuter)

[Domleschg]

Does "grün-weißes" mean that the shirt is one color, a greenish white, or that it has both colors - for instance, that it is green-and-white striped?

[wataya]

"Grün-weiß" means that both of the colors are present. But note that for neighboring hues like "blaugrün" a color somewhere in between blue and green is meant. Similarly, "rotbraun" means a reddish brown.

EDIT: In the past there was a rule that mixed colors (greenish white) were written as one word grünweiß while combinations of distinct colors (green and white) were written with a hyphen grün-weiß. This rule was very handy and I don't know exactly why it isn't mandatory anymore. Nonetheless, you can still use it, that's what I do and that's what I recommend. If you want to make it absolutely unambiguous that you are talking about a greenish white, just say "grünlich weiß".