Learn Swedish: Vilken färg väljer du? - Which color do you choose?

The word for "which" has to match the gender and number of the noun it belongs to. Since färg (color) is an en-word and it is singular here (just one color), we use vilken. If it were an ett-word, we would use vilket, and for plural words, we would use vilka.

Why is the word order väljer du instead of du väljer?

In Swedish questions, the verb often swaps places with the subject. This is because of the "verb second" rule. The question phrase Vilken färg takes up the first spot in the sentence, so the verb väljer must come immediately after it in the second spot, followed by the subject du.

Where is the word for "do" in this question?

Swedish does not use "do" to ask questions like English does. Instead of saying "Which color do you choose?", Swedish speakers simply say "Which color choose you?" (Vilken färg väljer du?).

What is the dictionary form of the verb väljer?

The dictionary form (infinitive) is välja (to choose). To make it present tense, the final -a changes to -er, giving us väljer.