There is no such thing as a 'coat of arms for a surname'. Many people of the same surname will often be entitled to completely different coats of arms, and many of that surname will be entitled to no coat of arms.
Coats of arms belong to individuals.
For any person to have a right to a coat of arms they must either have had it granted to them or be descended in the legitimate male line from a person to whom arms were granted or confirmed in the past. There are no fixed shades for heraldic colours. It is a popular misconception that the word 'crest' describes a whole coat of arms or any heraldic device. It does not. See the labelled illustration of a full achievement of arms here .