Blocks below tinted glass appear black

That is because tinted glass blocks light much like a regular block would if placed there. The reason that the block underneath is completely dark is because that block is getting a light level of zero. Hope this explanation makes sense.

Translation to better English:
This is because tinted glass blocks let light through like a regular block would if placed there instead. The reason the block underneath is completely dark is because the block is getting a light level of zero; there is no light passing through.

I tried the same thing and this does not happen in my device, so I think it has to be a graphics card issue.