Yes, precisely. -ú/-ű is a suffix that turns a noun into an adjective. Strictly spoken, rózsaszín is the colour itself, but that's also often used in place of the adjective.
A bit more on the suffix: There are multiple suffixes to make adjectives out of nouns. -ú/-ű is one that takes a quality that the object already has and modifies it. The car already has a colour, so we just define it more and slap the -ű at the end. A "barnaszemű lány" is a brown-eyed girl. A "háromlábú asztal" is a three-legged table.
Yes, after vowels it becomes -jú/-jű, but that happens rather rarely. I found the fun word épelméjű in my dictionary, meaning "mentally normal":
- ép - normal, intact, healthy
- elme - mind
The "regular colours" don't take the -ú/-ű suffix because they are already adjectives. Zöld stays zöld, but you can make compound words to describe people and objects with it, which take the suffix, then:
- zöldszínű - green-coloured
- zöldhajú - green-haired
- zöldszemű - green-eyed
- zöldtetejű - green-roofed
- zöldfülű - green-eared (a newbie)
épelméjű sounds like a perfectly normal word to me. At least the negation is quite common in news about crimes where the suspect is maybe not mentally fit for society.
This separates Verbrecher/ criminal/ bűnöző from (geistig abnorme) Rechstbrecher/ (mentally abnormal) lawbreaker (correct term?)/ ... .
No idea how to say that in Hungarian.
I found "éptelenelméjű" with exactly one google hit so i guess "nem épelméjű" is better? I have no other idea how to negate it otherwise.
Google suggests: szellemileg rendellenes törvényszegés.
Which does not use this word anyway. But searching for that gives then no hit... although it does not sound totally wrong. Szellem rend törveny szeg, mind order law break.
zöldfülű, noob, does exist in German too. But it is either "green behind the ears" (which seems to also exist in English and not just the "wet beh..." form) or greenhorn (Grünschnabel - greenbeak) and i don't know if English allows greenhorned but grünschnäbelig is possible.
Heyho, I should get back on this, so I can finally close this tab. It's a bit outside my expertise, but I'll take a stab at it.
There are a lot of terms for mentally ill people, but most often they are called in the vein of, well, "mentally ill" or "psychologically disturbed". In German, "geisteskrank", "psychisch gestört", or "seelisch krank" or any mix of these. In Hungarian you can say "mentálisan beteg" ("mentally ill") or "lelkileg zavart" ("soul-ly disturbed") or a mix of these.
You can negate épelméjű by replacing the adjective suffix with the negator suffix: épelmétlen ("healthy-mind-less"). That gives you 5 hits on Google already. "Nem épelméjű" seems to be the better choice still. :´D
Remember that the negator suffix -tlan/-talan doesn't typically go on an adjective (like ép), but on a noun or verb to make it into an adjective:
- igazság - truth (noun) > igazságtalan - untrue
- lehet - to be possible (verb) > lehetetlen - impossible
Saying "greenhorned" in English is possible, but most often you'll just use the noun. "Kid's a greenhorn." "She's a greenhorn programmer."
It can refer to either possibility, but most likely the speaker is talking about cars that are pink and cars that are purple. If I really want to refer to cars that are both pink and purple, I'd use a relative clause "Azok az autók nem szépek, amelyek rózsaszínűek és lilák is." Or just "A rózsaszínű-lila autók..."
I do not know what intention the creator of this sentence had, since it is a quite ambiguous sentence, but if I would like to do some real hair-splitting, I would say that s/he referred to cars that are both pink and purple, otherwise s/he would say:
A lila és a rózsaszínű autók nem szépek.