kono hutatu no syasin wo kuraberu to, sora no iro ga sukosi tigaimasu.

It is read:

この ふたつ の しゃしん を くらべる と、そら の いろ が すこし ちがいます。

In standard writing, it would normally be written without spaces:

この二つの写真を比べると、空の色が少し違います。

No. Japanese is normally written without spaces between words:

この二つの写真を比べると、空の色が少し違います。

The spaces here are just a learning aid to help you see the parts of the sentence more easily.

この is used before a noun.
これ is used by itself.

So:

• この写真 = this photo
• これ = this

Because 写真 comes right after it, この is the correct choice.

Yes, 二枚の写真 would also be very natural, and in some contexts even more precise.

The difference is:

• 二つ = a general counter for things
• 二枚 = the counter for flat objects, like paper, photos, plates, shirts, etc.

So:

• この二つの写真 = these two photos
• この二枚の写真 = also these two photos, but using the more specific counter for flat objects

Using 二つ is not wrong; it is just more general.

の connects nouns.

In this sentence, it appears twice:

• 二つの写真 = two photos
  Literally, something like photos of two / two-photo set
• 空の色 = the color of the sky or the sky’s color

A very common way to think of A の B is:

• B of A
• A’s B
• sometimes just a noun modifier, depending on context

So here:

• 空の色 = sky color = the color of the sky

Because 写真 is the direct object of the verb 比べる.

• 比べる = to compare
• What are you comparing? この二つの写真
• So the object takes を

That gives:

この二つの写真を比べる = compare these two photos

Here, と does not mean and.

In 比べると, the と means something like:

• when
• if
• once
• when you compare...

So:

この二つの写真を比べると、空の色が少し違います。
= When you compare these two photos, the color of the sky is a little different.

This と often connects one clause to a natural result or observation.

Because 空の色 is the thing that is different.

The sentence is not saying to differ the sky’s color.
It is saying the sky’s color differs.

So:

• 空の色 = the color of the sky
• が marks it as the subject of 違います

A natural breakdown is:

• この二つの写真を比べると = when you compare these two photos
• 空の色が少し違います = the color of the sky is a little different

少し means a little or slightly.

So:

• 違います = is different / differs
• 少し違います = is a little different

It softens the statement and shows that the difference is small, not dramatic.

違います is the polite form.
違う is the plain dictionary form.

So:

• 違う = plain
• 違います = polite

Likewise:

• 比べる is already in dictionary form because it appears before と
• the sentence ends politely with 違います

This mix is normal. In Japanese, only the final verb usually shows the overall politeness level of the sentence.

Good question. 違う / 違います can mean both:

• to be different
• to be wrong

Here, the meaning is clearly to be different, because we are comparing two photos:

空の色が少し違います = the color of the sky is a little different

If someone says 違います by itself in conversation, it often means That’s not right or No, that’s wrong, depending on context.

Yes, but it would slightly change the focus.

The original:

空の色が少し違います
focuses on the sky’s color as the thing that is different.

If you said:

空の色は少し違います

that would feel more like:

As for the sky’s color, it is a little different.

Both can work, but が is very natural here because it identifies what differs when the photos are compared.

Yes, Japanese word order is somewhat flexible, as long as the particles stay attached to the right words.

For example, these are all possible:

• この二つの写真を比べると、空の色が少し違います。
• この二つの写真を比べると、少し空の色が違います。
• 空の色が、この二つの写真を比べると、少し違います。
  (less natural in ordinary speech, but grammatically possible)

The original sentence is the most straightforward and natural for learners.

Yes. Japanese often leaves out information that is understood from context.

For example, English might say:

• When you compare these two photos, the color of the sky is a little different.
• If you compare these two photos, you can see that the color of the sky is a little different.

Japanese does not need to say you. It is understood from context.

So the sentence feels natural even though it does not explicitly name the person doing the comparing.