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HTML

              
                <H1>Color Contrast &amp; Mix</h1>

<p>Here we see several Web Components that are identical and have one property we pass on to a single custom property in CSS.</p>
<p>This property sets the text color, and only the text color.
	The color contrast function looks at the <code>--text-color</code> and compares this to a set of colors.
	For this I've created three sets of colors (primary, secondary and tertiary) and a contrast color for each set.</p>
<p>There are two mixed colors that each use two of the contrast color sets. And these two mixed values create the gradient that is applied to the web component. Also one mixed color is used to set the background color surrounding the gradient. </p>
<p><strong>Note</strong>: This is highly experimental and is subject to change. You can view this pen in Safari TP with color-contrast enabled and in Chrome with experimental web features enabled.</p>

<test-card data-color="blue"></test-card>
<test-card data-color="yellow"></test-card>
<test-card data-color="purple"></test-card>
<test-card data-color="pink"></test-card>
<test-card data-color="black"></test-card>
<test-card data-color="white"></test-card>

<template>
	<style>
		@import "https://unpkg.com/open-props";
		@import "https://unpkg.com/open-props/normalize.min.css";

		/* Properties */
		:host {
			--black: black;
			--white: white;
			/* Primary */
			--red: var(--red-9, red);
			--yellow: var(--yellow-4, yellow);
			--blue: var(--blue-7, blue);
			/* Secondary */
			--orange: var(--orange-8, orange);
			--green: var(--green-9, green);
			--purple: var(--violet-9, purple);
			/* Tertiary */
			--pink: var(--pink-4, pink);
			--teal: var(--teal-6, teal);
			--grape: var(--grape-9, grape);
			/* Note: incorrect references in a list of colors invalidates the entire list. */
			--primary-list: var(--red), var(--yellow), var(--blue);
			--secondary-list: var(--orange), var(--green), var(--purple);
			--tertiary-list: var(--pink), var(--teal), var(--grape);
			--contrast-01: color-contrast(var(--text-color) vs var(--primary-list) to AAlarge);
			--contrast-02: color-contrast(var(--text-color) vs var(--secondary-list));
			--contrast-03: color-contrast(var(--text-color) vs var(--tertiary-list));
			--mix-01: color-mix(in oklch,
					var(--contrast-01) 66.6666%,
					var(--contrast-02));
			--mix-02: color-mix(in oklch,
					var(--contrast-02) 66.6666%,
					var(--contrast-03));
			--gradient: linear-gradient(var(--contrast-01), var(--contrast-02));
			--background-color: var(--contrast-01);
			--card-display: grid;
			--card-columns: 1fr;
			--card-padding: var(--size-3, 1rem);
		}

		@supports (color: color-mix(in oklch, yellow 50%, navy)) {
			:host {
				--mix-01: color-mix(in oklch,
						var(--contrast-01) 66.6666%,
						var(--contrast-02));
				--mix-02: color-mix(in oklch,
						var(--contrast-02) 66.6666%,
						var(--contrast-03));
				--gradient: linear-gradient(320deg, var(--mix-02) 10%, var(--mix-01) 100%);
				--background-color: var(--mix-02);
			}
		}

		/* Rules */
		:host {
			display: block;
			padding-block: var(--multicol-gap, 0);
			break-inside: avoid;
			container: component / inline-size;
			flex: 1;
			min-width: min(20rem, 100%);
			color: var(--text-color);
			background-color: var(--background-color);
		}

		article {
			margin: 3rem;
			display: var(--card-display);
			grid-template-columns: var(--card-columns);
			gap: var(--gap);
			padding: var(--card-padding);
			background: var(--toggle-gradient, var(--gradient));
			color: var(--text-color);
		}

		h2 {
			margin: 0;
			color: var(--text-color);
		}

		/* Overrides */
		article:has(h2) {
			--card-padding: var(--size-7, 2rem);
		}

		@container component (min-width: 35em) {
			article {
				--card-columns: 1fr 1fr;
			}
		}
	</style>
	<article>
		<h2></h2>
		<p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Tempore ducimus autem illo quidem nobis aperiam cupiditate quia excepturi quos.</p>
	</article>
</template>
              
            
!

CSS

              
                h1,
p {
	margin: 0.5em 4rem;
}
p:last-of-type {
	margin-block-end: 3rem;
}
code,
pre {
	display: inline;
}

              
            
!

JS

              
                function markup() {
	const template = document.querySelector("template");
	const h2 = template.content.querySelector("h2");
	h2.innerText = this.color;
	console.log(template.content);
	return template.content.cloneNode(true);
}

class TestCard extends HTMLElement {
	constructor() {
		super();
		this.attachShadow({ mode: "open" });
		this.compTitle = this.dataset?.compTitle || ``;
		this.color = this.dataset?.color || ``;
		this.style = `--text-color:var(--${this.color})`;
		this.shadowRoot.appendChild(markup.call(this));
	}
}
customElements.define("test-card", TestCard);

              
            
!
999px

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