Hún ætlar að láta snyrta hárið og lita það aðeins fyrir brúðkaupið.

Ætla að + infinitive means to intend to, to plan to, or often to be going to.

So Hún ætlar að... means that she has the intention or plan to do something. It is a little more about intention than a simple neutral future.

The að belongs with ætlar:

• ætla að + infinitive = intend to / plan to

So we get:

• hún ætlar að láta...

After láta, Icelandic normally uses a bare infinitive:

• láta snyrta
• láta lita

So að láta snyrta is correct, but að láta að snyrta would be wrong.

Here láta is being used in a causative sense. That means to have something done or to get something done, not simply to let.

So:

• láta snyrta hárið = have the hair trimmed/styled
• láta lita það = have it colored/dyed

This is very similar to English expressions like have her hair done or get her hair colored.

Usually, no. It normally suggests that someone else will do it, for example a hairdresser.

That is one of the main things láta + infinitive often tells you: the subject causes the action to happen, but is not necessarily the person performing it.

If she were doing it herself, Icelandic would more naturally say something like:

• Hún ætlar að snyrta og lita hárið sitt.

Because both verbs are dependent on láta.

The structure is:

• ætlar að láta + infinitive
• and here there are two coordinated infinitives:
  • snyrta
  • lita

So the sentence means she plans to have [someone] trim/style the hair and color it.

Snyrta is a somewhat broad verb. With hair, it can mean tidy, trim, groom, or sometimes style the hair.

It does not always mean a full haircut in the strongest sense. It often sounds a bit softer or more general than simply saying cut the hair.

So in this sentence, it suggests making the hair look neat or presentable, probably as part of wedding preparation.

That ending is the attached definite article.

So:

• hár = hair
• hárið = the hair

and

• brúðkaup = wedding
• brúðkaupið = the wedding

Icelandic often attaches the to the end of the noun instead of using a separate word.

Because Icelandic often uses just the definite noun for body parts or personal belongings when the owner is obvious from the context.

So snyrta hárið can naturally mean do her hair here, because the subject is hún and it is clear whose hair is meant.

If you wanted to emphasize it, you could say hárið hennar, but it is not necessary.

Það refers back to hárið.

Since hár is a neuter singular noun, the pronoun used for it is það.

So instead of repeating hárið, Icelandic uses the pronoun:

• snyrta hárið og lita það

This is just like English saying trim the hair and color it instead of repeating the hair.

Aðeins can mean only, just, a little, or slightly, depending on context.

In this sentence it softens the idea of coloring the hair. It can suggest something like:

• just color it a bit
• color it only slightly
• just have it colored

So the exact nuance depends on context, but the general feeling is that the coloring is limited, small, or not too dramatic.

Here it means before the wedding.

So it places the action in time: she plans to have this done before the wedding.

Even though fyrir can have several meanings in Icelandic, in this sentence the natural reading is temporal.

Yes. That is completely normal.

The sentence structure is:

• ætlar að láta [snyrta hárið] og [lita það]

So one láta governs both actions. In other words, she plans to have both things done: the hair will be trimmed/styled and also colored.

You could repeat láta, but it is unnecessary:

• Hún ætlar að láta snyrta hárið og láta lita það...

That version is grammatical, but the original is more natural and economical.