I think many/most/all clams are like that, my electric blue squamosa looks 10x as bright from the top as the side.For some reason when you view the clam from the front like normally it looks dark blue. But when you view it from the top looking down it looks like the picture above.
Why is that?
Nah don't think the glass is causing issues with the clam colours here ...its also due to the glass. hence why starfire glass is highly sought after :)