How to control three LEDs with two uC pins using just passive components?
To control four LEDs:







simulate this circuit &ndash; Schematic created using CircuitLab

To get both LEDs on a particular pin lit, toggle the pin at a few hundred Hz.

Note that this setup requires that the forward voltage of the LEDs be less than Vcc/2.

Note also that the resistors consume power all of the time, not just when the LEDs are on.