PS2 cases in Australia at least have come in a variety of colours.
First and foremost you have the typical PS2 blue.
Second you have the platinum / silver cases for all platinum titles.
Third you do have black cases for some games, primarily the earlier titles.
I've also seen red cases for a few games like Legacy of Kain, Gran Turismo 3. I've also had clear cases for the Metal Gear Solid series.
I think that's pretty much the extent of colour variety. What region are you from Umbra? I know there's a seller in Australia that sells the same colour blue dvd cases that can be used as replacements. It's like 40 bucks shipped for 100.