Learn Hardcore Chinese: Nǐ shàngbān děi chuān lánsè de yīfu ma? - Do you have to wear blue clothes to work?

得 (děi) = have to/must (spoken, fairly strong, sounds like a personal or situational necessity).
要 (yào) = need to/going to; can mean obligation in context but is a bit softer and more general.
必须 (bìxū) = must; strongest and more formal/legalistic (rules, regulations). Examples:
你上班得穿蓝色的衣服。= You have to wear blue at work.
你上班要穿蓝色的衣服。= You need to/are supposed to wear blue at work.
你上班必须穿蓝色的衣服。= You must wear blue at work (strict rule).

How do I negate this idea? Is it 不得?

To negate a “must” as “not necessary,” use:

不用穿 / 不必穿 / 不需要穿 (don’t need to wear). If you mean “must not” (prohibited), use:
不能穿 / 不可以穿 (not allowed to wear), or formal 不得穿 (must not). Note: 不得 is not the simple negation of 得(děi); it means a prohibition.

Is this 得 the same as the one in degree complements like 走得快?

No. There are three common “de” particles:

得 (děi, 3rd tone): modal “have to” (this sentence).
得 (de, neutral) after verbs/adjectives for complements: 说得很快 (speaks quickly).
的 (de, neutral) for attributives: 蓝色的衣服 (blue clothes).
地 (de, neutral) for adverbials: 慢慢地走 (walk slowly).

Why is there a 的 after 蓝色? Can I say 蓝色衣服 or 蓝衣服?

蓝色的衣服 is the most standard attributive form.
蓝色衣服 (dropping 的) is common in speech; acceptable.
蓝衣服 uses 蓝 (blue) directly as an adjective; also natural. Nuance is minor:
蓝色的衣服 sounds slightly more careful/explicit.
蓝衣服 is a bit terser, more colloquial.

Do I need a measure word, like 一件?

Not necessarily. 衣服 can be a general mass noun:

你上班得穿蓝色的衣服吗？= Do you have to wear blue clothes/a blue outfit? If you mean one specific item:
你上班得穿一件蓝色的衬衫吗？(one blue shirt) Common classifiers: 一件衣服/衬衫, 一条裤子, 一双鞋, 一顶帽子.

Is 蓝色的衣服 singular or plural?

Chinese nouns are generally number-neutral. 蓝色的衣服 could mean “blue clothes,” “a blue outfit,” or “a blue garment.” Context clarifies. Use classifiers for specificity.

Why is 上班 placed right after 你? Can it move?

It’s an adverbial (occasion/time) and commonly goes before the modal/verb:

你上班得穿蓝色的衣服吗？(natural) Other natural options:
你在上班的时候得穿蓝色的衣服吗？ Avoid: 你得上班穿蓝色的衣服吗？(sounds off; add 的时候: 你得在上班的时候穿…)

Does 上班 mean “to go to work” or “to be at work”?

Both, depending on context. Here it means “when (you are) at work / for your job.” To make it explicit:

你上班的时候得穿蓝色的衣服吗？= Do you have to wear blue when you’re at work?

Is 穿 the right verb for “wear”? What about hats, glasses, ties?

穿: clothes, pants, shoes, socks (衣服、裤子、鞋、袜子).
戴: accessories (帽子 hat, 眼镜 glasses, 手表 watch, 手套 gloves).
系/繫 (jì/xì): ties, belts (领带、皮带).
穿着 (chuānzhuó): be wearing (continuous state).
So for general “clothes,” 穿 is correct.

How do I answer this yes–no question naturally?

Yes:
- 要/得。 (Yeah, I have to.)
- 要穿/得穿。
- 对，得穿蓝色的衣服。
No:
- 不用/不必。
- 不用穿/不必穿。
- 不需要穿。 If prohibited: 不能穿 / 不可以穿。

Can I ask without 吗 using the A‑not‑A form?

With 得(děi), A‑not‑A is awkward. Use other modals:

你上班要不要穿蓝色的衣服？
你上班需不需要穿蓝色的衣服？ You can also use:
你上班是不是得穿蓝色的衣服？

What’s the difference between this sentence and dropping 得: 你上班穿蓝色的衣服吗？

With 得: asks about a requirement/obligation (must).
Without 得: asks about a habit/fact (do you wear blue at work?). Choose based on whether you’re asking about rules vs. personal practice.

If the rule is “you must not wear blue,” how do I say that?

Conversational: 你上班不能穿蓝色的衣服。
Polite/soft: 不可以穿蓝色的衣服。
Formal rule: 上班不得穿蓝色的衣服。

Any pronunciation tips here (tones, neutral tones)?

得 (děi) is 3rd tone.
的 (de) and 吗 (ma) are neutral tone.
穿 (chuān) is 1st tone.
Tone sandhi: a 3rd tone is often realized as a “half‑third” before a non‑3rd tone; just keep děi low‑rising before chuān.

Is 你得在上班穿蓝色的衣服吗 okay?

Not natural. Use:

你在上班的时候得穿蓝色的衣服吗？
你上班得穿蓝色的衣服吗？ If you want a place rather than time:
你在公司得穿蓝色的衣服吗？

If I want to be more specific (e.g., shirt or uniform), how can I say it?

Shirt: 你上班得穿蓝色的衬衫吗？
Uniform: 你上班得穿蓝色的制服吗？
Suit/set: 你上班得穿一套蓝色的西装吗？ (classifier 套 for sets)

Can I drop the subject 你?

Yes, if context is clear:

上班得穿蓝色的衣服吗？ Chinese often omits subjects when they’re understood from context.