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Kathai aankhon wali ek ladki, ek hi baat par bigadti hai
Tum mujhe kyun nahi mile pehle, roz kehke mujhse ladti hai

(Rough English translation: The brown-eyed girl, gets upset by only one thing; Why didn’t you meet me sooner, she asks me this everyday. Link to the song: http://www.youtube.com/watch?v=iB3wB8cRE88)

This beautiful line was penned by Javed Akhtar for the film Duplicate. Ever wondered what the lafz ‘kathai’ means. It describes the beautiful brown coloured eyes of the girl and adds a twang of lyricism to an otherwise simple line.

Below are the Urdu names for different colours:
Black سیاہ siyáh
White سفيد Safaid
Red لال، سرخ surḳh
Pink گلابى Gulábí
Orange نارنگی nárangí
Saffron کیسریا، زعفران kesirayá, záfrán
Yellow پیلا، زرد pílá, zard
Green ہرا، سبز hará, sabz
Blue نيلا Nílá
Light Blue/sky blue آسمانی Ásmání
Turquoise فیروزی Ferozí
Purple بینگنی، جامنی، اودا bainganí, jámní, údá, arghwani
Brown بھورا Bhúrá, kathai
Almond coloured بارامک Badami
Gray سلیٹی، سرمئی sleṭí, surmaí
Silver چاندی، روپہلا chándí, rúpahalá
Golden سنہرا Sunahará
Shiny چمکیلا Chamkílá
Source: Wikipedia

Another interesting colour-related word is ‘unnaabi’ (انابک) which is the reddish-brown colour of mashed grapes (Unnabi in Urdu means grape) and is typically used to describe the colour of blushed cheeks, or when someone is embarrassed. (Source: Saadat Hasan Manto’s short story ‘Mozail’)

Some more additions, courtesy fellow Urduwallah, Sophia Andre Kapadia:

violet: banafshii-بنفشی
mauve: kaasnii-کاسنی
blue : aabi آبی 
cochineal/dusty pink : Pyaazi
Bright magenta: Rani

A couplet with ‘kaasnii’ | Faiz Sahib writes in his poem “pass raho”:
Tume mere paas raho…Dard kai kaasni pazeb bajaati niklay (Stay near me….when (the night) comes out wearing mauve / steel-blue anklets, ringing with grief)

Source: http://forum.wordreference.com/showthread.php?t=2058320