Sometimes Photoshop is a damn fool and you need an export process that sucks less at color palette selection and dithering.

gif_process-electric_leaves.js

//REQUIREMENTS: The following programs must be installed and accessible in your PATH
//	node > 6
//	imagemagick's command line tool "convert"
//	giflossy - which can be installed with `npm install -g giflossy`, but only on mac and linux??
//USAGE: Change params at the top to your liking. `node gif_process.js` starts it up.
//	EXECUTES ALL TASKS IN PARALEL.
//	If you run it like this, it will CONSUME YOUR WHOLE COMPUTER (100% cpu, 100% memory) for a few minutes while it works.
//DISCLOSURE: I was running terribly low on sleep when I wrote this. It's a tool. It gets a job done like ten times ever. Don't judge me on this. The code I write for my day job is like way better and I care a lot more about it because I have to maintain it all the time.
//LICENSE: MIT

let imPath = 'script_output-imagemagick/';
let gsPath = 'script_output-giflossy/';
let seriesName = 'electric_flower';
let inputPngFolderList = [
	'08-comp_a',
];
let outputParams = [ //<-- only do like 1 set at a time for sanity
	{width: 1920, height: 1080},
	{width: 1080},
	{width: 960, height: 540, lossy: 10},
	{width: 480, lossy: 10},
	{width: 480, height: 270, lossy: 5},
	{width: 400, colors: 128, lossy: 35},
	{width: 400, height: 225, colors: 256, lossy: 5},
];
let sourceWidth = 1920;
let sourceHeight = 1080;
let sourceAspect = sourceWidth / sourceHeight;
let backgroundColor = '#000000';

/*------------------------------------------------*/

const fs = require('fs');
const child_process = require('child_process');

let makePath = function(path){
	if(!fs.existsSync(path)){
		fs.mkdirSync(path);
	}
};
makePath(imPath);
makePath(gsPath);

let timeTask = function(taskName, callback){
	var start = Date.now();
	return function(err, stdout, stderr) {
		var time = (Date.now() - start);
		console.log([taskName, stdout, time, 'ms'].join(' ').replace(/\n/g, ' '));
		if (err) {
			console.error(err);
			return;
		} else if(callback) {
			callback();
		}
	};
};

let hellYeahGifProcess = function(x, y, scale, c, l){
	let width = x;
	let height = y || x;
	let resize = scale || width > height ? width : height;
	let colors = c || 256;
	let lossy = l || 0;
	let targetAspect = width / height;

	let leftRight = (width - resize) / 2;
	let topBottom = (height - resize) / 2;

	let scaledCount = 0;

	let sourceCropWidth = Math.ceil(targetAspect * sourceHeight);
	let sourceCropHeight = Math.ceil((targetAspect * sourceHeight) / targetAspect);
	let leftRightCrop = (sourceWidth - sourceCropWidth) / 2;
	let topBottomCrop = (sourceHeight - sourceCropHeight) / 2;
	let crop = `-crop ${sourceCropWidth}x${sourceCropHeight}+${leftRightCrop}+${topBottomCrop}`;

	let dimensionsLabel = `${width}x${height}`;
	if(scale){
		dimensionsLabel += `x${scale}`;
	}
	if(c){
		dimensionsLabel += `-colors_${c}`;
	}
	let imSizePath = imPath + dimensionsLabel + '/';
	let gsSizePath = gsPath + dimensionsLabel + '/';
	makePath(imSizePath);
	makePath(gsSizePath);

	let imList = [];
	let gsList = [];
	let gifSicleImagesWhenDone = function(){
		imList.forEach(function(outputFileNameIM, index){
			let outputFileNameGS = gsList[index];
			let lossyArg = lossy ? `--lossy=${lossy}` : '';
			child_process.exec(
				[
					'giflossy',
					'-O3',
					lossyArg,
					`-o ${outputFileNameGS}`,
					outputFileNameIM
				].join(' '),
				timeTask(outputFileNameGS)
			);
		});
	};

	let onComplete = function(){
		scaledCount++;
		if(scaledCount === inputPngFolderList.length){
			gifSicleImagesWhenDone();
		}
	};

	inputPngFolderList.forEach(function(inputFileName){
		let name = `${seriesName}-${inputFileName}-${dimensionsLabel}`;
		let nameLossy = lossy ? `-lossy_${lossy}` : '';
		name += '-imagemagick';
		let outputFileNameIM = imSizePath + name + '.gif';
		let outputFileNameGS = gsSizePath + name + `-giflossy${nameLossy}.gif`;
		let argument = [
			'convert',
			'-dispose 2',
			'-delay 1/24',
			inputFileName + '/*.png',
			'-coalesce',
			crop,
			'-resize ' + resize,
			`-background "${backgroundColor}"`,
			'-alpha remove',
			`-bordercolor "${backgroundColor}"`,
			//`-border ${leftRight}x${topBottom}`,
			'-dither FloydSteinberg',
			//'-ordered-dither o8x8,64',
			//'-ordered-dither o2x2,128,128,64',
			//'-ordered-dither checks,128',
			`-colors ${colors}`,
			'+repage',
			outputFileNameIM
		].join(' ');
		console.log(argument);
		imList.push(outputFileNameIM);
		gsList.push(outputFileNameGS);
		child_process.exec(
			argument,
			timeTask(outputFileNameIM, onComplete)
		);
	});
};

outputParams.forEach(function(params){
	hellYeahGifProcess(params.width, params.height, params.resize, params.colors, params.lossy);
});