Gold plate color difference

Speaking of gold plate, I have a question about two gold-plated
pieces of kitchenware which I found in my travels.

One is a bowl, said to be 22 carat gold plated according to the
label. The other is a gold plated cup said to be 24 carat gold. The
22 carat plating is a dull yellow which seems to be what pure gold is
but the 24 carat is a darker, almost reddish yellow.

Does anybody have an idea as to what causes the difference?

The karat on plating solutions refers to the color rather than
actual karat, manufacturers may have different interpretations of
color.

Color is affected by several things besides the original formula.
Plating temperature. Plating voltage. Base metal. Time in bath. Anode
choice. Plating appearance can change over time.

Does anybody have an idea as to what causes the difference? 

Gold in thin layer is transparent. What you see is the color of a
background affecting appearance of a gold layer.

Leonid Surpin