Dropping a stained glass item on a transparent block makes the glass inside the current Air color
Environment
Computer: Acer Aspire 7750g
Windows 7 (x64) (Sp1)
Java 1.7.0_17 (x64)
Minecraft Launcher 1.3.11
RAM: 4 GB (3,85 GB can be used)
Processor: Intel core i3 - 2.30 GHz
Graphic card: AMD Radeon HD 7670M, 1 GB VRAM
Intended.