element-plus/website/color.js

export const tintColor = (c, tint) => {
  const color = c.replace('#', '')
  let red = parseInt(color.slice(0, 2), 16)
  let green = parseInt(color.slice(2, 4), 16)
  let blue = parseInt(color.slice(4, 6), 16)

  if (tint === 0) {
    // when primary color is in its rgb space
    return [red, green, blue].join(',')
  } else {
    red += Math.round(tint * (255 - red))
    green += Math.round(tint * (255 - green))
    blue += Math.round(tint * (255 - blue))
    red = red.toString(16)
    green = green.toString(16)
    blue = blue.toString(16)
    return `#${red}${green}${blue}`
  }
}