You can add an extra layer between the text and background where you apply the opacity:

.box {
  padding:10px;
  display:inline-block;
  color:var(--c);
  background:var(--c);
  position:relative;
  z-index:0;
}

.box::before {
  content:"";
  position:absolute;
  z-index:-1;
  top:0;
  left:0;
  right:0;
  bottom:0;
  background:rgba(255, 255, 255, 0.5);
}

<div class="box" style="--c:red">some text</div>

<div class="box" style="--c:blue">some text</div>

<div class="box" style="--c:green">some text</div>

Same idea without pseudo element:

.box {
  padding:10px;
  display:inline-block;
  color:var(--c);
  background:var(--c);
  
  background-image:linear-gradient(rgba(255, 255, 255, 0.5),rgba(255, 255, 255, 0.5))!important;
}

<div class="box" style="--c:red">some text</div>

<div class="box" style="color:blue;background:blue;">some text</div>

<div class="box" style="color:green;background-color:green;">some text</div>

You can use the color NPM package to do that:

import Color from 'color';

const colorWithOpacity = Color(yourColor).alpha(yourOpacity).rgb().string();

You will need to adjust your code to pass colorWithOpacity to your styles.

I have an object with a set of information, including color. I intend this color to be implemented as a background-color with opacity and as a text color (without opacity to look different).

Does anyone know how I can make it so that through the color of the object / variable, I can add opacity?

DEMO

.ts

color: string = "green";
name:string = "ABC";
id: number = 1;

.html

<div style="display: flex; flex-direction: column; width: 60%;">
        <span [style.background-color]="color" [style.color]="color" class="cc">{{name}}</span>
        <span [style.background-color]="color" class="mb" [style.color]="color">{{id}}</span>
    </div>

Problem

I want the background-color to have opacity so that the text is visible. I intend to achieve this, without having to create a variable with a “different” color.