docs: Add reference for CSS value serialization, especially colors

[Shrinivassab]

Add reference for CSS value serialization, especially colors

Fixes #32734

Description

Adds a new guide explaining CSS value serialization through JavaScript APIs, with a focus on how color values (hsl(), hwb(), etc.) are serialized to rgb()/rgba() format when accessed via getComputedStyle() or getPropertyValue().

Motivation

This documentation helps developers understand why and how CSS values, especially colors, might return in different formats than they were written. This addresses a common source of confusion when working with CSS values through JavaScript APIs.

Additional details

References:

• CSSOM Specification - Serializing CSS Values
• CSS Color Module Level 4 - Serialization

Related issues and pull requests

Fixes #32734 - Creates documentation for CSS value serialization, especially for colors

[github-actions]

Preview URLs

• /en-US/docs/Web/API/CSS_Object_Model/Serializing_CSS_values

Flaws (3)

URL: /en-US/docs/Web/API/CSS_Object_Model/Serializing_CSS_values
Title: Serializing CSS values
Flaw count: 3

• broken_links:
  • /en-US/docs/Web/CSS/Using_CSS_custom_properties is a redirect
• unknown:
  • Error serializing baseline for numeric-seperators: missing field description``
  • Error serializing baseline for single-color-gradients: missing field description``

External URLs (2)

URL: /en-US/docs/Web/API/CSS_Object_Model/Serializing_CSS_values
Title: Serializing CSS values

• https://drafts.csswg.org/css-color-4/ (1 time) (Note! This may be a new URL 👀)
• https://drafts.csswg.org/cssom/ (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2025-09-29 04:05:11)

[Josh-Cena]

A lot of content is incomplete or duplicative. I suspect you are using AI to write this, which is fine in principle, but next time please disclose this because it's not the quality we are expecting for a ready-for-review PR. Also, you should document length serialization as well at least, since that's the other common use case.

[Shrinivassab]

Hi @Josh-Cena , Yes, I tried the Co-pilot version of Sonnet 3.5. I will keep it in mind to mentioned that in the PR, I was not sure, if we used Copilot need to raise as Draft PR or Ready to reviewPR.

[Shrinivassab]

Let me know if any changes need to be updated or any grammatical error . Happy to update it. Thanks for the review.