Program two pins to do the same thing....

The passed array could be defined two-dimensional, that would give a beginner an easy way to select the eye by index. I would pass pointers for the manipulating functions anyway.

Huh, array? I don't see an array... ::)

The array that contains the RGB data? Probably allocated by

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

There is none? While usinge NeoPixels?

I use FastLED and in that library you get a pointer to the data by calling a member function

    // returns pointer to the CRGB buffer for the first strip
    CRGB *leds() { return (*this)[0].leds(); }

Guys thank you very much. I come from the Plc world so this is very different to me. I seem to be having an issue understanding what the error messages actually mean. Believe me I tried changing the line that turned pink ( error on that line??) many times before reposting. Thanks again will try again when home.