I started to construct a diagram in Fritzing to explain how the wiring for the above worked, but it soon became as covered in wire as the real thing. So, attached is a diagram showing just the green and orange channels and I hope it's easy enough to extrapolate from there.
Each group of 4 LEDs shares a direct connection to one pin without a resistor, with the 4 anodes linked. Then the other legs are connected via a resistor to the other colours in the sequence green, orange, white, blue, yellow (always in this order, but omitting of course the colour that the anodes are).
So the green group has green to the anodes, then the cathodes in left to right sequence are orange, white, blue & yellow. The orange group has orange to the anodes, with green, white, blue & yellow to the cathodes left to right. White group's cathodes are sequenced green, orange, blue & yellow; the blue group's cathodes go green, orange, white & yellow; and the yellow group's cathodes go green, orange, white & blue.
I found colour coding made setting out the breadboard very simple, but repetitive. I started with the row of 20 LEDs, each with the flat side to the right. Once constructed a simple sketch walking the LEDs down the array on the Uno was used to test it, then I moved the connections to the ATTiny85 on the breadboard.
HTH, Geoff
