В settings.js parallaxMultiplier: 10
Возможно particles.js у них модифицированный немного.
$('#particles').particleground({
dotColor: 'rgba(255, 255, 255, 0.92)',
lineColor: 'rgba(255, 255, 255, 0.1)',
minSpeedX: 0.1,
maxSpeedX: 0.6,
minSpeedY: 0.1,
maxSpeedY: 0.6,
lineWidth: 1,
density: 12100, // One particle every n pixels
curvedLines: false,
proximity: 150, // How close two dots need to be before they join
parallaxMultiplier: 10, // Lower the number is more extreme parallax
particleRadius: 3, // Dot size
});
UPD:
Там не particles.js а particleground