Vi ska sortera kläderna efter färg.

Ska is used to talk about a planned, intended, or expected future action.

So:

• Vi ska sortera kläderna efter färg = We are going to sort the clothes by color
• Vi sorterar kläderna efter färg = We sort / are sorting the clothes by color

In many everyday sentences, ska is very close to English going to. Depending on context, it can also suggest obligation, like shall / are supposed to, but here it most naturally means a plan.

After modal verbs like ska, Swedish uses the infinitive form of the main verb.

So:

• ska sortera
• kan sortera
• vill sortera
• måste sortera

Not:

• ska sorterar

This is similar to English:

• will sort
• can sort

not will sorts.

After modal verbs such as ska, kan, vill, and måste, Swedish normally does not use att.

So:

• Vi ska sortera kläderna = correct
• Vi ska att sortera kläderna = incorrect

You can think of it like English we are going to sort, not we are going to to sort.

Kläderna means the clothes.

It breaks down like this:

• kläder = clothes
• kläderna = the clothes

The ending -na is the definite plural ending here. Swedish often adds definiteness to the end of the noun instead of using a separate word before it.

Because Swedish usually puts the definite article onto the noun itself.

So English:

• the clothes

becomes Swedish:

• kläderna

This is very common in Swedish:

• bok = book
• boken = the book
• hus = house
• huset = the house
• kläder = clothes
• kläderna = the clothes

If there is an adjective, Swedish often uses both a separate article and the ending:

• de röda kläderna = the red clothes

Kläder is plural, just like English clothes.

Swedish normally does not use a singular kläd in everyday language to mean a clothing item. For one item, you would usually say:

• ett plagg = a garment / an item of clothing
• ett klädesplagg = an article of clothing (more formal)

So:

• kläder = clothes
• kläderna = the clothes

Usually, efter often does mean after, but in this sentence it means according to or by.

So sortera efter färg means:

• sort by color
• sort according to color

This is a very common use of efter when talking about classification or criteria.

Other similar examples:

• ordna efter storlek = arrange by size
• sortera efter namn = sort by name

Here färg is being used in a general, category-like way: by color.

After efter, Swedish often uses a bare singular noun when talking about the basis for sorting, organizing, or comparing:

• efter färg = by color
• efter storlek = by size
• efter namn = by name

Why not the other forms?

• en färg would sound like a color as one specific color
• färgen would sound like the color, one particular color
• färger means colors, but that is less natural in this fixed kind of expression

Also, färg is an en-word:

• en färg
• färgen

But in this sentence, no article is needed.

The sentence follows normal Swedish main-clause word order:

• Vi = subject
• ska = finite verb
• sortera = infinitive
• kläderna = object
• efter färg = prepositional phrase

So the structure is:

subject + finite verb + infinitive + object + other information

A very important rule in Swedish is that the finite verb usually comes in second position in main clauses. So if something else comes first, ska still stays second:

• Imorgon ska vi sortera kläderna efter färg. = Tomorrow we are going to sort the clothes by color.

Not:

• Imorgon vi ska sortera...

A rough guide:

• kläderna sounds roughly like KLEH-der-na
• färg sounds roughly like fair-y with a very short ending, though this is only an approximation

A few notes:

• ä is like the vowel in English air or bed, depending on accent and word
• g at the end of färg is not pronounced like a strong English g
• Swedish pronunciation varies somewhat by region

If you want to sound natural, it helps to learn the whole rhythm:

• Vi ska sortera kläderna efter färg

with the stress mainly on -te- in sortera, klä- in kläderna, and färg.