HTML email dark mode still inverts brand colors in Gmail and iOS Mail despite all known protections

I am building a transactional HTML email (not marketing) where brand color fidelity is critical.
The email is generated server-side (Node.js) and uses a strictly table-based layout for maximum compatibility.

The company’s primary brand colors are yellow and blue, and preserving those exact colors is mandatory.

The problem

When the email is viewed in dark mode, some colors are still automatically inverted or overridden by the email client:

Gmail (iOS and Android) — most frequent

iOS Mail — intermittent

Gmail Web — occasionally

In light mode, the email renders exactly as intended.

This behavior appears client-driven, not caused by missing CSS support.

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What I have already implemented

I have intentionally implemented every currently documented mitigation:

Layout

Table-only layout (no div, flex, or grid)

Fixed 600px container with max-width:100%

No external CSS

No background images for brand-critical areas

Color protection

Inline styles on every element

bgcolor attributes on all <table> and <td> elements

Explicit triple declarations (bgcolor, background-color, color)

No shorthand CSS

Dark mode handling

<meta name="color-scheme" content="light dark">

<meta name="supported-color-schemes" content="light dark">

@media (prefers-color-scheme: dark) overrides

[data-ogsc] selectors for Outlook.com / Outlook apps

Explicit dark-mode classes where adaptation is acceptable

Client considerations

-webkit-text-size-adjust

Apple Mail reformatting disabled

PNG icons only (no SVG)

Tested on

Gmail iOS / Android

iOS Mail

Outlook.com

Outlook Desktop

Apple Mail (macOS)

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What still happens

Despite all of the above:

Some background colors are inverted

Some text colors are overridden

This happens inconsistently, but most often in Gmail

Brand colors are affected, not just neutral backgrounds

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Core question

Is there any truly reliable, deterministic way to fully prevent color inversion in HTML emails on Gmail and iOS Mail?

Or is this behavior fundamentally unavoidable due to proprietary dark-mode rendering heuristics implemented by email clients?

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Follow-up (industry practice)

If full prevention is impossible:

What is the recommended production approach in 2025?

Single adaptive template that tolerates partial inversion?

Two separate templates (light + dark)?

Hybrid approach where only brand sections are “locked”?

I am specifically interested in real-world, production-proven strategies, not theoretical CSS support.

white mod:

dark mod:

For anyone who wants to see the code or do some tests, I'll leave it here:

https://drive.google.com/file/d/1Pv8itXvqIDKBknjkiPztgWwtQj3vsFZj/view?usp=sharing