Learn Hardcore Japanese: kare ha meganeya de kuroi hureemu wo eranda ga, watasi nara mousukosi akarui iro ni suru darou. - He chose black frames at the eyeglasses shop, but if it were me, I would probably choose a slightly brighter color.

メガネ屋 – casual, everyday word; what people normally say in conversation.
メガネ店 (めがねてん) – sounds a bit more formal or business-like (you might see it in store names, written ads, etc.).

Using just メガネ would mean “glasses” themselves, not the shop, so you need 屋 to show it’s a store.

What does the particle で in メガネ屋で do? Why not use に?

で marks the place where an action happens.

メガネ屋で = “at the glasses shop / in the glasses shop”

In this sentence, 選んだ (chose) is the action, and it happens at the shop, so で is used.

に would be used more for:

the destination: メガネ屋に行く – “go to the glasses shop”
the existence of something: メガネ屋に人がいる – “There are people in the glasses shop”

For “doing an action at a place,” で is the normal choice:

学校で勉強する – study at school
レストランで食べる – eat at a restaurant
メガネ屋で選ぶ – choose (something) at a glasses shop

What is the function of が in 選んだが、私なら…? Is it the subject particle?

Here が is not the subject marker. It is a conjunction meaning “but / although.”

選んだが、 = “(he) chose (it), but …”

So the structure is:

彼はメガネ屋で黒いフレームを選んだが、
私ならもう少し明るい色にするだろう。

= “He chose black frames at the glasses shop, but if it were me, I would go with a slightly brighter color.”

So:

Subject marker が: after a noun (e.g., 彼が選んだ)
Conjunction が: after a verb/adjective clause (e.g., 選んだが)

Why is フレーム followed by を? What is を doing here?

を marks the direct object of the verb.

黒いフレームを選んだ
“(He) chose black frames.”

Here:

黒いフレーム = “black frames”
選んだ = “chose”
を shows that “black frames” is what he chose.

So the pattern is:

[object] を [action verb]
- 本を読む – read a book
- コーヒーを飲む – drink coffee
- 黒いフレームを選んだ – chose black frames

Why is the first part past tense (選んだ) and the second part するだろう? Why are tenses mixed?

The sentence contrasts:

What he actually did (past fact)
What I would do (hypothetical preference)

選んだ = past tense: “(he) chose”
するだろう = “would do / would probably do”

So:

彼は…選んだ – “He chose …”
私なら…にするだろう – “If it were me, I’d (probably) choose … / I would go with …”

Mixing past for the real action and “would” form for the hypothetical speaker’s choice is natural, and Japanese reflects that with 選んだ vs. するだろう.

What does なら in 私なら mean? How is 私なら different from 私は?

なら often means “if / in the case of / as for (if we’re talking about)”.

私なら = “If it were me,” or “As for me, in my case, I would…”

Nuance:

私は – just marking the topic: “I …”
私なら – introduces a hypothetical version of me or a contrast: “If we’re talking about what I would do (as opposed to what he did)…”

In this sentence:

彼は黒いフレームを選んだ
= He chose black frames.
私ならもう少し明るい色にするだろう
= If it were me, I’d go with a slightly brighter color.

So なら emphasizes “in my case / if I were in that situation” and sets up the contrast.

What does もう少し mean here? Is it “already a little” or “a little more”?

もう少し (もうすこし) here means “a little more / a bit more / somewhat more.”

もう can mean “more / further” (not only “already”)
少し = a little / a bit

So:

もう少し明るい色 = “a little brighter color”
(compared to what he chose)

It implies:

His choice is somewhat dark.
The speaker would choose something a bit lighter in color.

Why is it 明るい色にする and not 明るい色をする? What does に do with する here?

This is the common pattern X にする, which means:

“to make something X”
or
“to decide on / choose X” (in a selection situation like shopping or ordering).

In this sentence:

明るい色にする = “to go with a bright color / to choose a bright color.”

Pattern:

[choice / final state] + にする

Examples:

コーヒーにします。– I’ll have coffee. / I’ll go with coffee.
部屋をきれいにする。– Make the room clean.
このデザインにする。– I’ll go with this design.

So 色にする doesn’t literally mean “to do color”; it’s “to make it that color / to choose that color.”
That’s why it’s 色にする, not 色をする.

What nuance does だろう add in するだろう? How is it different from just する?

だろう adds a sense of conjecture / probability / “would probably” and also softens the statement.

する (plain) = “(I) will do / (I) do / (I) would do” (more direct)
するだろう = “(I) would probably do / I’d likely do”

Here, it’s expressing a hypothetical, not absolute statement:

私ならもう少し明るい色にする。
= If it were me, I’d choose a slightly brighter color. (fairly direct)
私ならもう少し明るい色にするだろう。
= If it were me, I would probably choose a slightly brighter color. (softer, more tentative)

So だろう makes it sound a bit less blunt, more like giving an opinion.

Why is it 明るい色 and not something like 明るいフレーム? Is 色 just “color” here?

Yes, 色 (いろ) literally means “color.”

明るい色 = “a bright/light color”
The frame itself is understood from context (we’re talking about glasses frames), so Japanese often just mentions the color:
- “I’d go with a brighter color (for the frames).”

You could say:

明るいフレーム – bright-colored frames

…but it sounds a bit redundant in this context. Japanese frequently drops what’s obvious and just says 色.

Why do the adjectives come before the nouns, like 黒いフレーム and 明るい色? Is that always the pattern?

Yes, in Japanese adjectives normally come before the noun they modify.

黒いフレーム = black frames
明るい色 = bright color

This is the standard pattern:

大きい家 – big house
古い本 – old book
新しいメガネ – new glasses
黒いフレーム – black frames
明るい色 – bright color

So this word order is the normal one:
[adjective] + [noun].

Is this sentence casual or polite? How would you say it politely?

The sentence as given is casual/plain style:

選んだ (plain past)
するだろう (plain conjectural)

To make it polite, you’d normally use ます/でした forms and soften the ending a bit:

彼はメガネ屋で黒いフレームを選びましたが、
私でしたらもう少し明るい色にすると思います。

For example:

選んだ → 選びました
私なら → 私でしたら (politer conditional)
するだろう → すると思います (more polite/soft)

There are several polite variations, but the key change is moving from plain to ます forms.