Photoshop:
- File -> New (CTRL+N) (use transparent background)
- select a region,
- fill it with some color,
- double-click on the layer (on the right bottom)
- apply a Bevel or a Shadow effect,
- add a new layer,
- put under the previous one,
- merge layers (CTRL+SHITF+E)
- save your image as .png

#K: the shortcut won't answerd to click/mouseover; but the label/whatever under it will !