As far as I could tell, my strands were defective. I worked with the company I bought them from and I sent them back and got a refund.
I believe I have some rather bad
news for you.
Your posting has provoked me into setting up a chain of these "pixels" that I purchased a few months back, which having wrangled the libraries - an educational experience in itself encountering some less than helpful instructions on the Adafruit pages confusing upper and lower case - I now have joyfully chasing and surging up (and down) my bookcase. Well, bully for me, but clearly pleasing. (OK, they have started to worry me - now turning them off!)
The point is
- the behaviour you describe, of the first pixel turning on when you apply power, and changing colour when you touch the wiring, is entirely normal
and in fact
demonstrates that the pixels are in perfect order.
I have to conclude then that in your case, the control input lines were simply not connected
to the Arduino. They are high impedance (CMOS) inputs and will readily pick up random interference, even radio signals in some cases.
How this could have happened is then the question. If you connect the data outputs instead to the Arduino, then the input wires at the other end
would be sensitive to this interference. (The data output wire is buffered, so holding it down does not affect the input.) You apparently did try swapping end for end.
I have checked various cases of the pin behaviour on the Arduino. With the Arduino off (no power), all ports are necessarily pulled down to ground and cannot float. While they do float in reset, and with an alternate sketch that does not define the pins to which you have connected the pixels, I am unable to generate any interference to "spook" the pixels when they are turned on under these circumstances.
I have to conclude therefore that the behaviour you describe indicates no code fault, normally functional
pixels, but that the connections of the pixel chain control inputs (possibly including the ground) were simply not made
however that may have happened.
(And I trust just in case, that you did
try swapping the green and yellow wires as a test.)