Flop this to make a button that is depressed. No, not blue, but in the un-up position. I've added some shading so you can see both the smaller square and the two halves of the square beneath. Here are the three button states using the square button. As the mouse passes over the button, the button appears to rise up.
Many software applications can create a conical gradient fill.
This is a gradient fill that sweeps 360 degrees from a central point. Reversing the light and dark portions of the fill create a recessed button. As with the square buttons, here are the three round button states. The Initial state is in the recessed position while the Over state is raised. The Out state is raised and is the same color as the Initial state but the text is a different color.