helium/ui: match Chrome tab group colors for better contrast

[jakeleventhal]

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Tested on (check one or more):

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Screen.Recording.2026-05-21.at.8.23.52.PM.mov

Adds better tab color group contrast. The labels are hard to read sometimes as demonstrated by #1536 (comment).

Closes:

• [FR]: pastel color support in tab group #1536
• [FR]: Better tab group appearance #1179

[AleyaDevelopment]

I am curious if it makes sense for this to be a config instead of hard coded? I could see this being in chrome://flags with the option for a user to override with their preferred color scheme.

[jakeleventhal]

I am curious if it makes sense for this to be a config instead of hard coded? I could see this being in chrome://flags with the option for a user to override with their preferred color scheme.

I think here it's better to go with Steve Jobs' approach in this case. Good defaults are often better than overly-customizable experiences. It's the customer's job to validate the design, not make it themselves.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "helium/ui: match Chrome tab group colors" | Re-trigger Greptile}

[greptile-apps]

Tab strip frame colors hardcoded to pastel 300-level regardless of light/dark mode

The original code used ui::SelectBasedOnDarkInput(kColorTabBackgroundInactiveFrameActive, k*300, k*600) — 300-level for dark tab backgrounds and 600-level for light ones. The new code unconditionally assigns {tg::k*300} for every kColorTabGroupTabStripFrameActive* and kColorTabGroupTabStripFrameInactive* slot. In Helium's light mode (toolbar is SK_ColorWHITE), the 300 pastels (e.g. kBlue300 = #8AB4F8 against a white/near-white tab strip) produce noticeably lower contrast than the 600-level colors they replaced (e.g. kBlue600 = #1A73E8). The same concern applies to kColorTabGroupDialog* which previously inherited from kColorTabGroupContextMenuBlue (light/dark adaptive) but now also points to flat {tg::k*300}. This could undo the contrast improvement the PR aims to deliver for light-mode users.