Indeed it is, but one can find very cheap Tricolour LEDS on Ebay (although of questionable quality).
I am also using 74HC595 shift registers to control the rows so I only need 3 dedicated pins
.
However your suggestion requires some serious looking into as i am bit banging 16 bits at a time for row control, whilst a cursory glance at the spec sheet for the 74LS138 indicates 3 bits can control 8 lines rather than using 8 bits for 8 lines, which means less processing, and hence i might be able to cut down on the slight flicker that is apparent in my display.
Perhaps connecting a shift register to the demultiplexer control pins will avoid using if statments inside my drawing loop and a simple spiout will suffice, or i can use the
let pins = b0 command
Thanks for the pointer.