Ružičasta haljina joj dobro stoji, dok je narančasta jakna toplija za jesen.

Joj is the dative singular form of ona (she/her), and here it means to her.

So:

• Ružičasta haljina joj dobro stoji = The pink dress looks good on her / suits her well

Croatian often uses the dative with verbs like stajati when talking about how clothes look on someone.

You could also say:

• Ružičasta haljina dobro joj stoji

That still means the same thing; the clitic just moves position according to normal Croatian word-order rules.

Yes, literally stajati means to stand, but with clothing it often means:

• to suit someone
• to look good on someone
• to fit someone well (in a visual/style sense, not necessarily size)

So:

• Haljina joj dobro stoji = The dress suits her / looks good on her

This is a very common expression in Croatian.

Compare:

• Ova boja ti dobro stoji. = This color suits you.
• Ta jakna mu ne stoji baš dobro. = That jacket doesn’t suit him very well.

Because both nouns are feminine singular nominative, and the adjectives have to agree with them.

• haljina = feminine singular
• jakna = feminine singular

So the adjectives are also feminine singular:

• ružičasta haljina
• narančasta jakna

This is normal Croatian adjective agreement: adjectives match the noun in gender, number, and case.

Here dok means something like:

• while
• whereas
• while on the other hand

In this sentence it introduces a contrast:

• Ružičasta haljina joj dobro stoji, dok je narančasta jakna toplija za jesen.

So the idea is:

• the pink dress suits her well,
• whereas the orange jacket is warmer for autumn.

This is not mainly about two actions happening at the same time; it is more about comparing two facts.

Because je is a clitic, and Croatian clitics usually go in the second position in their clause.

In the clause:

• dok je narančasta jakna toplija za jesen

the first element is dok, so the clitic je comes immediately after it.

This second-position behavior also affects words like:

• je, su
• sam, si, smo, ste
• se
• short pronouns like joj, mu, ti, mi

This is one of the most important word-order patterns in Croatian.

Toplija is the comparative form of topla / topao (warm).

So:

• topao = warm
• topliji / toplija / toplije = warmer

Here it agrees with jakna, which is feminine singular, so the form is:

• toplija

Full phrase:

• narančasta jakna toplija = the orange jacket is warmer

The comparative is used because the sentence is implicitly comparing the jacket with the dress, or generally comparing options.

This is just how that adjective forms its comparative. Some Croatian adjectives have stem changes.

For topao:

• masculine: topliji
• feminine: toplija
• neuter: toplije

So the l appears in the comparative stem: topl-.

This is something learners usually just memorize through exposure.

Za jesen means for autumn in the sense of:

• suitable for autumn
• intended for autumn
• good for autumn weather

So:

• jakna je toplija za jesen = the jacket is warmer for autumn

Here za expresses purpose/suitability, and it takes the accusative:

• jesen = accusative singular here

By contrast:

• u jesen usually means in autumn / during autumn

So the meanings are different:

• toplija za jesen = better suited for autumn
• toplija u jesen = warmer in autumn

Because the noun jesen has the same form in nominative singular and accusative singular.

Since za here requires the accusative, the form is still:

• jesen

So even though the case changes grammatically, the word itself does not look different in this instance.

Yes, Croatian word order is fairly flexible, but not completely free. You can move things around for emphasis, especially nouns and adjectives, but clitics like joj and je still follow special placement rules.

For example, you could also say:

• Ružičasta joj haljina dobro stoji, dok je narančasta jakna toplija za jesen.
• Narančasta je jakna toplija za jesen, dok joj ružičasta haljina dobro stoji.

These versions shift emphasis a bit, but the basic meaning stays similar.

Yes, but the meaning would change slightly.

• dobro stoji = suits her / looks good on her
• dobro izgleda = looks good
• odgovara joj = suits her, fits her needs, is appropriate for her
• pristaje joj = suits her (also common, especially for appearance)

For clothing and appearance, both dobro stoji and pristaje joj are very natural.

Example:

• Ružičasta haljina joj dobro stoji.
• Ružičasta haljina joj pristaje.

Both are good, but stoji is especially common for how clothes look on someone.

Yes. They are adjectives and behave like regular adjectives, so they change to agree with the noun.

Here they are feminine singular because they describe feminine nouns:

• ružičasta haljina
• narančasta jakna

If the noun were masculine, you would get:

• ružičasti kaput
• narančasti šal

And with neuter:

• ružičasto odijelo
• narančasto svjetlo

So color words in Croatian usually work just like other adjectives.

It has two coordinated parts joined by dok:

1. Ružičasta haljina joj dobro stoji
2. dok je narančasta jakna toplija za jesen

So the pattern is roughly:

• [subject] + [indirect object clitic] + [adverb] + [verb]
• dok + [clitic] + [subject] + [predicate]

In natural English terms, it is contrasting two qualities:

• the dress is more flattering,
• the jacket is more practical for autumn.

That kind of contrast is very common in Croatian.