Ons onderskei rooi van blou.

In this sentence, ons means we.

Afrikaans ons can also mean us, depending on its role in the sentence. Afrikaans does not change the form the way English does.

• Ons onderskei rooi van blou. = We distinguish red from blue.
• Hy sien ons. = He sees us.

So you have to tell from the sentence whether ons means we or us.

Because Afrikaans verbs usually do not change for person.

In English, we say:

• I distinguish
• he distinguishes
• we distinguish

In Afrikaans, the verb normally stays the same:

• Ek onderskei
• Hy onderskei
• Ons onderskei

This is one reason Afrikaans grammar is often simpler than English in this area.

Onderskei means to distinguish, to tell apart, or sometimes to differentiate.

In this sentence, it means being able to recognize the difference between two things:

• Ons onderskei rooi van blou. = We distinguish red from blue. = We can tell red apart from blue.

So the idea is not just naming colors, but noticing the difference between them.

In this sentence, van means from, just like in English distinguish X from Y.

So:

• rooi van blou = red from blue

This pattern is very natural in Afrikaans:

• onderskei iets van iets anders = distinguish something from something else

So van is not possessive here. It is part of the expression showing separation or difference.

Because here rooi and blou are being used as color concepts, not as specific nouns with articles.

Compare:

• Ons onderskei rooi van blou. = We distinguish red from blue.

This works like English, where you also usually do not say the red from the blue in this meaning.

If you were talking about specific objects, articles might appear:

• Ons onderskei die rooi motor van die blou motor. = We distinguish the red car from the blue car.

So in your sentence, the colors are used in a general sense.

They are color words being used on their own, so they function more like nouns here, even though they are also commonly adjectives.

As adjectives:

• 'n rooi motor = a red car
• 'n blou hemp = a blue shirt

On their own:

• rooi
• blou

In Ons onderskei rooi van blou, the words stand alone and refer to the colors themselves: red and blue.

Yes. This is normal main clause word order in Afrikaans:

• Ons = subject
• onderskei = verb
• rooi van blou = rest of the sentence

So the structure is: Subject + Verb + Object/Complement

That is very similar to English:

• We distinguish red from blue.

Afrikaans word order becomes more different from English in subordinate clauses, but this sentence is straightforward.

A rough English-friendly guide is:

Ons onderskei rooi van blou
≈ ons on-duh-SKAY roy fon bloh

A few notes:

• ons sounds roughly like ons with a short vowel
• onderskei ends with -skei, which sounds like skay
• rooi sounds roughly like roy
• van is often said more lightly than English van
• blou sounds like blow, but with an Afrikaans vowel quality

Pronunciation varies by speaker and region, but this approximation is enough to get started.

Yes, absolutely.

• Ons onderskei rooi van blou.
• Ons kan rooi van blou onderskei.

The second version adds kan = can, so it means:

• We can distinguish red from blue.

In everyday usage, the version with kan may sound especially natural when you want to stress ability.

Because kan is a modal verb, onderskei moves to the end:

• Ons kan ... onderskei

That is a very common Afrikaans pattern.

Yes. Onderskei is used much more broadly.

It can mean:

• distinguish
• differentiate
• tell apart

Examples:

• Ek kan sy stem van haar stem onderskei. = I can distinguish his voice from her voice.
• Ons moet feite van menings onderskei. = We must distinguish facts from opinions.

So the sentence with colors is just one example of a very general verb.

It is correct and idiomatic.

A native speaker might also say:

• Ons kan rooi van blou onderskei.
• Ons kan tussen rooi en blou onderskei.

But Ons onderskei rooi van blou is perfectly good Afrikaans and clearly expresses the idea.

The exact version chosen depends on context:

• plain statement: Ons onderskei rooi van blou
• emphasis on ability: Ons kan rooi van blou onderskei
• emphasis on choosing between two things: Ons kan tussen rooi en blou onderskei

The basic verb is onderskei.

Afrikaans often uses te before an infinitive in certain constructions, but not always.

Examples:

• Ons probeer rooi van blou onderskei. = We try to distinguish red from blue.
• Dit is moeilik om rooi van blou te onderskei. = It is difficult to distinguish red from blue.

So yes, onderskei can appear with te, but in your original sentence it is a normal finite verb, so no te is used.