[... light-emitting diode display ...]
David Wijnants writes, "http://www.xs4all.nl/~arjenvm/pics/index.html has lots of icons 'n stuff, including red and green 'bullets'. Just stick a .GIF image on a canvas, or in a label, and switch images when you need to - for example :
image create photo red -file smb_red.gif
image create photo green -file smb_green.gif
pack [ label .led -image red -height 50 -width 50 ]
pack [ button .red -text Rood -command { .led configure -image red
} ] -fill x
pack [ button .green -text Groen -command { .led configure -image green
} ] -fill x
With Mark G. Saye's package [L1 ], "you can create leds (labels) with different sizes and colors, and you can flash them (toggle bg/fg colors and normal/active states), disable (and resume) flashing. There's even a demo for Knight Rider fans."