This is the 2229th most frequent Arabic word.
الأحمر
Red.
Here, 'الحمراء' is an adjective in the feminine form describing the noun 'السيارة' (car), which is feminine in Arabic.
السيارة الحمراء تسير بسرعة.
The red car is moving fast.
In this sentence, 'حمراء' is used as a predicate adjective describing the state of the subject 'الشمس' (the sun), agreeing in gender.
الشمس حمراء عند الغروب.
The sun is red during sunset.
Here, 'الأحمر' is a noun referring to the color red, in the definite form (the red), showing a general concept.