WS2812B LED strip and ESP8266 shows wrong colors

@user85573, if by chance you have the setup, could you do some timing on these variations of the code and post the results?

Variation 1(a))

// V1a - flash an 8 LED neopixel array in a rainbow pattern
var led_count = 8;
var neoPin = NodeMCU.D4;
var rgb = new Uint8ClampedArray(led_count * 3);
var pos = 0;
function getPattern() {
  pos++;
  for (var i=0;i<rgb.length;) {
    rgb[i++] = (1 + Math.sin((i+pos)*0.1324)) * 127;
    rgb[i++] = (1 + Math.sin((i+pos)*0.1654)) * 127;
    rgb[i++] = (1 + Math.sin((i+pos)*0.1)) * 127;
  }
  return rgb;
}
setInterval(function() {
  var t0 = getTime();
  require("neopixel").write(neoPin, getPattern());
  console.log(getTime() - t0);
}, 200); // may need to change to allow console to write

Variation 2(a))

// V2a - flash an 8 LED neopixel array in a rainbow pattern
var neo = require("neopixel");
var led_count = 8;
var neoPin = NodeMCU.D4;
var rgb = new Uint8ClampedArray(led_count * 3);
var len = rgb.length;
var m = 127;
var r = 0.1324*m;
var g = 0.1654*m;
var b = 0.1*m;
var pos = 0;
function getPattern() {
  pos++;
  for (var i=0; i<len;) {
    rgb[i++] = m + Math.sin((i+pos)*r;
    rgb[i++] = m + Math.sin((i+pos)*g;
    rgb[i++] = m + Math.sin((i+pos)*b;
  }
  return rgb;
}
function bow() {
  var t0 = getTime();
  neo.write(neoPin, getPattern());
  console.log(getTime() - t0);
}

function onInit() {
  setInterval(bow,200); // may need to change to allow console to write
}

setTimeout(onInit, 1000);

And as begin curious what the calculation vs communication times are:

// V1b - flash an 8 LED neopixel array in a rainbow pattern
var led_count = 8;
var neoPin = NodeMCU.D4;
var rgb = new Uint8ClampedArray(led_count * 3);
var pos = 0;
function getPattern() {
  var t0 = getTime();
  pos++;
  for (var i=0;i<rgb.length;) {
    rgb[i++] = (1 + Math.sin((i+pos)*0.1324)) * 127;
    rgb[i++] = (1 + Math.sin((i+pos)*0.1654)) * 127;
    rgb[i++] = (1 + Math.sin((i+pos)*0.1)) * 127;
  }
  console.log(getTime() - t0);
  return rgb;
}
setInterval(function() {
  var t0 = getTime();
  require("neopixel").write(neoPin, getPattern());
}, 200); // may need to change to allow console to write

and

// V2b - flash an 8 LED neopixel array in a rainbow pattern
var neo = require("neopixel");
var led_count = 8;
var neoPin = NodeMCU.D4;
var rgb = new Uint8ClampedArray(led_count * 3);
var len = rgb.length;
var m = 127;
var r = 0.1324*m;
var g = 0.1654*m;
var b = 0.1*m;
var pos = 0;
function getPattern() {
  pos++;
  for (var i=0; i<len;) {
    rgb[i++] = m + Math.sin((i+pos)*r;
    rgb[i++] = m + Math.sin((i+pos)*g;
    rgb[i++] = m + Math.sin((i+pos)*b;
  }
  console.log(getTime() - t0);
  return rgb;
}
function bow() {
  neo.write(neoPin, getPattern());
}

function onInit() {
  setInterval(bow,200); // may need to change to allow console to write
}

setTimeout(onInit, 1000);

The results may shed some light on how coding in Espruino can matter for execution speed.

(The different start-up is not part of the timings. It just makes sure that the upload is not interfering)