How to set transparent color for my own AutoCAD icons?

If you need to create a partially "transparent" toolbar icons, you cannot use standard ways of PNG format with alpha-channel or transparent GIF files - AutoCAD supports only icons in the BMP format which doesn't work with transparency.

But you can use a trick - the color with the hue of 192-192-192 (RGB) used in icons is interpreted by AutoCAD as "transparent".