lab()

lab(29.2345% 39.3825 20.0664);
lab(52.2345% 40.1645 59.9971);
lab(52.2345% 40.1645 59.9971 / .5);

<div data-color="red"></div>
<div data-color="red-a"></div>
<div data-color="green"></div>
<div data-color="green-b"></div>
<div data-color="blue"></div>
<div data-color="blue-light"></div>

div {
  width: 50px;
  height: 50px;
  padding: 5px;
  margin: 5px;
  display: inline-block;
  border: 1px solid black;
}

[data-color="red"] {
  background-color: lab(100 125 125);
}
[data-color="red-a"] {
  background-color: lab(100 110 125);
}
[data-color="green"] {
  background-color: lab(75% -120 125);
}
[data-color="green-b"] {
  background-color: lab(75% -120 10);
}
[data-color="blue"] {
  background-color: lab(0 -120 -120);
}
[data-color="blue-light"] {
  background-color: lab(70 -120 -120);
}

<div id="background-div">
  <div data-color="red"></div>
  <div data-color="red-alpha"></div>
</div>

div {
  width: 50px;
  height: 50px;
  padding: 5px;
  margin: 5px;
  display: inline-block;
  border: 1px solid black;
}
#background-div {
  background-color: lightblue;
  width: 150px;
  height: 40px;
}

[data-color="red"] {
  background-color: lab(100 125 125);
}
[data-color="red-alpha"] {
  background-color: lab(100 125 125 / 0.4);
}