Some ADB AppleDesign keyboards do not properly signal the Power Macintosh G3 (Blue and White) to enter Open Firmware during startup.
Products affected:
AppleDesign keyboards identifiable by the ADB cable hardwired to the keyboard, have a stepped Caps Lock key, and say "AppleDesign" on the underside of the keyboard.
Solution:
Use the USB keyboard which came with your computer, or a different ADB keyboard.