Learn Farsi: این طوطی یک کاکل نرم و رنگارنگ دارد. - This parrot has a soft and colorful crest.

This sentence demonstrates syntactic coordination of adjectives. The head noun کاکل (crest) takes an Ezafe to link to its modifiers. However, because نرم (soft) and رنگارنگ (colorful) are joined by و (and), they form a single descriptive unit. You only need the Ezafe on the noun: کاکلِ نرم و رنگارنگ (kakol-e narm o rangarang). Adding an Ezafe to نرم would be grammatically incorrect because the words are parallel.

In spoken Farsi, how do native speakers pronounce the و in نرم و رنگارنگ?

While written as و (va), native speakers almost always pronounce it as a short 'o' sound when it links two adjectives. It attaches smoothly to the end of the first adjective, so you will hear 'narm-o rangarang' in everyday speech instead of 'narm va rangarang'.

How is the adjective رنگارنگ constructed?

It is created using a very common Farsi word-building pattern where a noun is repeated with the vowel 'a' (ا) inserted in the middle. Here, رنگ (color) plus ا plus رنگ creates رنگارنگ, which literally implies 'color to color' and translates to 'colorful' or 'multi-colored'.

Could we drop یک and use the indefinite suffix ی instead to say 'a crest'?

Yes, you absolutely can. You could say کاکلِ نرم و رنگارنگی (kakol-e narm o rangarang-i), attaching the indefinite to the very end of the adjective chain. Using at the beginning, as seen in this sentence, is an alternative way to mark the noun phrase as indefinite. At the B2 level, it is good to remember that both methods are natural, though can sometimes feel slightly more deliberate.