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chromate coating is designed to passivate the underlying coating to prevent it from oxidizing. Chromate is very difficult to control from an appearance point of view, the higher the concentration in the solution (an acid based solution with a lowish PH) the darker the resulting color. Chromate can leave a slightly gold tint up to a dark matt green hiding the underlying coating completely.

Some other factors that affect the look are:

break down of the solution (from Hexavalent to trivalent) resulting in yellow staining

wet storage too soon after coating resulting in a partial or complete loss of the coating

temperature and acidity of the solution affect color and shine also.

The principal thing to remember is that chromate is considered a temporary coating by design, to protect the underlying coating when it is fresh and therefore at risk of rapid oxidation before the cad or zinc can form a stable carbonate surface.

The above is from experience, I am in the coating business (unrelated to cars) for 25 years now and use chromate in our processes.