Learn Farsi: ما همیشه شلوار آبی یا سبز می‌پوشیم.

You would ask ما همیشه کدام شلوار را می‌پوشیم؟. As you learned in this lesson, کدام comes right before the singular noun it describes (شلوار), and you do not use the connecting ezâfe sound between them. (Notice we also added را because "which pants" becomes a specific direct object).

In English, "pants" is a plural word. Why is شلوار (shalvâr) singular here?

In Farsi, single items that happen to have two parts (like pants, glasses, or scissors) are grammatically singular. You only make شلوار plural (like شلوارها) if you are actually talking about multiple different pairs of pants.

How does the connecting ezâfe sound work when there are two adjectives connected by یا (or)?

You only use the ezâfe (the short "-e" linking sound) to connect the noun to the very first adjective: شلوارِ آبی (shalvâr-e âbi). Because the word یا (yâ) separates the two colors, you don't add another ezâfe onto the end of آبی. It is simply spoken as shalvâr-e âbi yâ sabz.

Does می‌پوشیم (mipushim) mean "we are wearing" or "we wear"?

It can mean both! The می (mi-) prefix forms the present continuous tense ("we are wearing") as well as the present habitual tense ("we wear"). Because the word (always) is used in this sentence, context makes it clear that this is the habitual "we always wear".