The standard method of chrome plating has in the past always used hexavalent solutions.
For various reasons related to toxicity and carcinogens (in the industry) alternatives have been sought and the use of trivalent solutions is one of the alternatives.
Apart from the colour difference trivalent solutions produce coatings that are slightly less wear and corrosion resistant than hexavalent.
This is a gross simplification but for a more technical (and informed) explanation please see here.
If you can't be bothered with the detail skip to the conclusion.
