Seeing colours in the Istikharah
Answer:
In the name of Allah, the most Beneficent, the most Merciful.
Istikharah is to seek guidance from Allah when one is faced with a problem.
It is related by Jabir bin Abdullah that the Prophet of Allah 
used to teach us the way of doing Istikharah, in all matters as he taught us the Surahs of the Quran... (Sahih Al-Bukhari, 2.263)
When making Istikharah a person should perform two Rakats Nafl Salat. Then with all sincerity recite the following Du’a.
Translation: O Allah!! Behold I ask You the good through Your Knowledge, and ability through Your Power, and beg (Your favour) out of Your infinite Bounty. For surely You have Power; I have none. You know all; I know not. You are the Great Knower of all things. O Allah! If in Your Knowledge this matter be good for my faith (Deen), for my livelihood, and for the consequences of my affairs, then ordain it for me, and make it easy for me, and bless me therein. But if in Your Knowledge, this matter be bad for my faith (Deen) for my livelihood, and for the consequences of my affairs, then turn it away from me, and turn me away therefrom, and ordain for me the good wherever it be, and cause me to be pleased therewith.
Imam An-Nawawi has said, “After performing the istikharah, a person must do what he is wholeheartedly inclined to do and feels good about doing and should not insist on doing what he had desired to do before making the istikharah. And if his feelings change, he should leave what he had intended to do, otherwise he is not completely leaving the choice to Allah, and would not be honest in seeking aid from Allah’s power and knowledge. Sincerity in seeking Allah’s choice means that one should completely leave what he himself had desired or determined.” (Fiqhus Sunnah: 2.32)
After performing istikarah the person will (Insha Allah) get guidance from Allah and be inclined towards what is right. It is not necessary that it is seen in a dream or even as a vision while awake. The individual will just feel what is right and should then go on to do the task or make the decision. Some scholars like Imam Ibn Abideen Shami 
have said that if one sees white or green in his dream then it is a guidance to do that thing. However, if one sees black or red he or she should refrain from it. (Raddul Muhtar p.471 v.2)
In conclusion as I mentioned above, the main thing is what you feel in your heart. If you feel contentment in your heart that this is good you should go ahead with it and Insha Allah there will be blessings in it.
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham