Try running the Neopixels off a LiPo battery - that's the easiest way to test. The ~4v voltage still works fine with the pixels but the voltage allows the 3.3v signal from the Pico to get through correctly.
Also worth checking - are the grounds of the two power sources connected? That's another potential culprit of the first green LED.
While 1v94 may work for you, in the ~18 months since that version other people have used Neopixels with Espruino Pico (me included - I just did exactly that with a Pico running 2v01 to make sure yet again) and it works absolutely fine.
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