The colors aren't changeable as the core parts are because Fritzing changes to the round led layout when anything changes, and I think a code change would be needed to change that. This came about because someone wanted stackable LEDs for an instructable and was having problems with wires overlaying the LEDs.
These differ mostly in size (closer to the breadboard) and connections (one lead on the top and bottom of the LED). Here are another set of rectangular LEDs similar to the set by Old_Grey.
