I’ve measured how quartz splits light into very subtle gradations, and that’s exactly what you need for an 8‑bit set—pick a base hue, then add a couple of lighter and darker tints that mimic the refraction. For amethyst, a soft lavender with a single bright magenta accent will give that sparkle without muddying the palette. Remember, pixel art thrives on contrast; too much subtlety and the sparkle will blur. If you send me a quick shot of your swatches, I can point out where the precision slips.