Learn Spanish (Spain): La mujer compra dos manzanas rojas.

No, most numbers in Spanish do not change based on gender. While the number one changes (un vs una), the number two is always dos, whether you are counting feminine things like manzanas (apples) or masculine things like perros (dogs).

Why is it manzanas rojas instead of rojas manzanas?

In English, describing words (adjectives) go before the noun, like "red apples". In Spanish, they usually come right after the noun they describe. So, the order is manzanas rojas (literally: apples red).

Why does the word for red, rojas, end in -as?

Adjectives must match the noun they describe in both gender (masculine or feminine) and number (singular or plural). Because manzanas is feminine and plural (more than one), the base word rojo changes to its feminine plural form, rojas.

What is the base form of the verb compra?

The base verb (the dictionary form) is comprar, which means "to buy". It is changed to compra here to match la mujer (the woman), which acts as a "she" (third-person singular) in the sentence.