Learn Arabic (Modern Standard): أرى سماء زرقاء جميلة.

In Arabic, colors have different patterns for masculine and feminine words. The masculine pattern is أفعل (like أزرق), but because sky (سماء) is a feminine noun, we must use the feminine pattern فعلاء. This changes the word to زرقاء.

Wait, how do we know سماء (sky) is feminine? It doesn't end with a standard feminine ending like a taa marbuta (ة).

You are right! While most feminine words end in a taa marbuta (ة), سماء is one of a few common nouns that are naturally feminine by exception. You can clearly see it is being treated as feminine in this sentence because both adjectives describing it (زرقاء and جميلة) are strictly in their feminine forms.

Why does the Arabic word order seem to be sky blue beautiful instead of beautiful blue sky?

In Arabic, adjectives always come after the noun they describe. When there are multiple adjectives modifying a single noun, the most permanent or essential quality (like the physical color زرقاء) is usually placed closest to the noun, followed by more subjective descriptions (like جميلة).

I don't see a word for a in this sentence. How do we know it means a beautiful blue sky?

Arabic does not have an indefinite article like a or an in English. When a noun and its adjectives do not have the definite article ال (the) attached to the beginning of them, it automatically translates to an indefinite meaning like a or an.