A variety of colors are mentioned in the Guru Granth Sahib including references to white, blue, red and yellow.
No specific color seems to take precedence over others and no dominant theme of color preference seems to emerge from the references in the Guru Granth Sahib. Many of the references refer to colors worn by members of the Muslim and Hindu religions.
White and Blue
Guru Arjan, pg. 885
koee parrai baedh koee kathaeb ||
Some read the Vedas, and some the Koran.
koee oudtai neel koee supaedh ||3||
Some wear blue robes, and some wear white. ||3||
Guru Nanak, pg. 470
saam kehai saetha(n)bar suaamee sach mehi aashhai saach rehae || sabh ko sach samaavai ||
The Sama Veda says that the Lord Master is robed in white; in the Age of Truth, everyone desired Truth, abided in Truth, and was merged in the Truth.
Same shabad later:
kal mehi baedh athharaban hooaa naao khudhaaee alahu bhaeiaa ||
In the Dark Age of Kali Yuga, the Atharva Veda became prominent; Allah became the Name of God.
neel basathr lae kaparrae pehirae thurak pat(h)aanee amal keeaa ||
Men began to wear blue robes and garments; Turks and Pat'haans assumed power.
Blue
Guru Nanak, pg. 16
neelee siaahee kadhaa karanee pehiran pair dhhiaan ||
The blackness of sin is erased by my wearing of blue clothes, and meditation on the Lord's Lotus Feet is my robe of honor.
Guru Nanak, pg. 471
neel vasathr pehir hovehi paravaan ||
Wearing blue robes, they seek the approval of the Muslim rulers.
malaeshh dhhaan lae poojehi puraan ||
Accepting bread from the Muslim rulers, they still worship the Puraanas.
Guru Nanak, pg. 902
kal kalavaalee saraa nibaerree kaajee kirasanaa hoaa ||
In this turbulent age of Kali Yuga, Muslim law decides the cases, and the blue-robed Qazi is the judge.
Red
Guru Arjan, pg. 384
laal cholanaa thai than sohiaa ||
That red dress looks so beautiful on your body.
surijan bhaanee thaa(n) man mohiaa ||1||
Your Husband Lord is pleased, and His heart is enticed. ||1||
Guru Amar Das, pg. 785
lokaa vae ho soohavee soohaa vaes karee ||
O people: I am in red, dressed in a red robe.
vaesee sahu n paaeeai kar kar vaes rehee ||
But my Husband Lord is not obtained by any robes; I have tried and tried, and given up wearing robes.
Guru Amar Das, pg. 786
soohaa ra(n)g vikaar hai ka(n)th n paaeiaa jaae ||
The red color is vain and useless; it cannot help you obtain your Husband Lord.
eis lehadhae bilam n hovee ra(n)dd bait(h)ee dhoojai bhaae ||
This color does not take long to fade; she who loves duality, ends up a widow.
mu(n)dhh eiaanee dhu(n)manee soohai vaes luobhaae ||
She who loves to wear her red dress is foolish and double-minded.
sabadh sachai ra(n)g laal kar bhai bhaae seegaar banaae ||
So make the True Word of the Shabad your red dress, and let the Fear of God, and the Love of God, be your ornaments and decorations.
naanak sadhaa sohaaganee j chalan sathigur bhaae ||2||
O Nanak, she is a happy soul-bride forever, who walks in harmony with the Will of the True Guru. ||2||
Yellow
Guru Arjan, pg. 1082
peeth peetha(n)bar thribhavan dhhanee ||
The Lord of yellow robes, the Master of the three worlds.
jaga(n)naathh gopaal mukh bhanee ||
The Lord of the Universe, the Lord of the world; with my mouth, I chant His Name.