Improve tab selected state contrast for vertical tabs

[simonhong]

Description

Hard to know which tab is selected

Steps to reproduce

1. Enable vertical tab
2. Create some tabs
3. Select tabs

Actual result

See the screen shot

Expected result

should have more noticable color for selected and inactive tab

Reproduces how often

Easily reproduced

Brave version (brave://version info)

1.73.9 Chromium: 130.0.6723.44 (Official Build) nightly (x86_64)

Channel information

• [x] release (stable)
• [x] beta
• [x] nightly

Reproducibility

• [ ] with Brave Shields disabled
• [ ] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

cc @rebron @bsclifton @aguscruiz

[MadhaviSeelam]

Reproduced the issue in Win 11 x64

Brave | 1.71.114 Chromium: 130.0.6723.58 (Official Build) (64-bit)
-- | --
Revision | 89c4031c685a4296315a6f421f46275f0b72dd55
OS | Windows 11 Version 23H2 (Build 22631.4317)

Light	dark	custom

[rebron]

Related: https://github.com/brave/brave-browser/issues/41450

[valynor]

This is not only affecting vertical tabs but regular tabs, too:

The selected pinned tab (Protonmail) is BARELY visible on a large monitor esp. when looked at off-axis. 1.71.114 Chromium: 130.0.6723.58 (Official Build) (arm64)

[Brave-Matt]

Yes I am seeing many users complain that in dark mode specifically it is too hard to tell which tab is selected: https://community.brave.com/t/new-horizontal-tab-design-is-excellent/507900/4 (just a few examples)

[aguscruiz]

Gonna be working on improving the contrast with @fallaciousreasoning over the next few days. This may be related too https://github.com/brave/brave-browser/issues/41720#event-14801938066

[aguscruiz]

Already fixed in Nightly

https://github.com/brave/brave-core/pull/26259