На тёмной блузке маленькая складка заметнее, чем на светлой.

Because на can take different cases depending on meaning.

Here it means on the blouse / on a light one, describing location, so Russian uses the prepositional case:

• тёмная блузка → на тёмной блузке
• светлая блузка → на светлой

If it meant motion onto something, then Russian would use the accusative:

• положить на блузку = to put onto the blouse

So in this sentence, the fold is located on the blouse, which is why the prepositional is used.

Because both adjectives agree with an implied feminine singular noun in the prepositional case.

The noun is блузка, which is:

• feminine
• singular
• prepositional after на in this meaning

So:

• тёмная блузка → на тёмной блузке
• светлая блузка → на светлой блузке

In the second part, блузке is omitted because it is already understood.

Because маленькая складка is the grammatical subject of the sentence.

The sentence is basically saying:

A small crease is more noticeable on a dark blouse than on a light one.

So складка is the thing being described, and маленькая agrees with it:

• складка = feminine singular nominative
• маленькая = feminine singular nominative

Заметнее means more noticeable, easier to see, or more visible in context.

It is the comparative form of заметный:

• заметный = noticeable
• заметнее = more noticeable

In this sentence, it functions as the main predicate:

• складка заметнее = the crease is more noticeable

This comparative form is very common in Russian and often works like an adverb or predicative adjective in English translation.

Because in the present tense, Russian normally omits the verb to be.

So where English says:

• The small crease is more noticeable

Russian simply says:

• Маленькая складка заметнее

This is completely normal. Russian does not usually use a present-tense equivalent of is in sentences like this.

Because Russian often omits a noun when it is obvious from context.

So:

• на тёмной блузке ... чем на светлой really means
• на тёмной блузке ... чем на светлой блузке

English does this too:

• on the dark blouse ... than on the light one

Russian simply leaves out the repeated noun.

Чем introduces the second part of a comparison, like than in English.

So:

• заметнее, чем на светлой = more noticeable than on the light one

This is the normal word used in comparisons:

• лучше, чем... = better than...
• быстрее, чем... = faster than...
• заметнее, чем... = more noticeable than...

Yes. Russian word order is flexible, though the original sentence sounds natural and neutral.

Original:

• На тёмной блузке маленькая складка заметнее, чем на светлой.

You could also say:

• Маленькая складка заметнее на тёмной блузке, чем на светлой.

Both are understandable. The original version puts early focus on where the crease is noticeable: on a dark blouse.

Russian word order often reflects emphasis rather than strict grammatical necessity.

It can mean several related things depending on context:

• fold
• crease
• pleat
• sometimes wrinkle

In this sentence, crease or fold is probably the best translation. Since it is about a blouse and visibility, small crease sounds very natural in English.

So the idea is that a small crease shows up more clearly on dark fabric than on light fabric.

Both are possible.

• маленькая = small
• небольшая = small, slight, not large

In many contexts they are close in meaning, but небольшая can sound a little more neutral or formal, while маленькая is the basic everyday word.

So:

• маленькая складка = a small crease
• небольшая складка = a slight/small crease

The sentence with маленькая is perfectly natural.

It can work either way depending on context.

Russian often does not use articles, so на тёмной блузке can mean:

• on a dark blouse
• on the dark blouse

And на светлой can mean:

• on a light blouse
• on the light one

The broader idea of the sentence is general: a small crease is more noticeable on dark clothing than on light clothing.

Yes, but the meaning and style shift a little.

Possible alternatives:

• складка заметнее = the crease is more noticeable
• складка более заметна = the crease is more noticeable

Both are grammatical. But заметнее is shorter, simpler, and usually more natural in everyday Russian.

Also note the difference in form:

• заметнее = comparative form
• более заметна = more
  • short-form adjective

The original sentence sounds very natural and idiomatic.