Issue 852896  has been merged into this issue.

nanjingchj@ Thanks for the issue.

Tested this issue on Windows 10 on the latest Canary 69.0.3463.0 and unable to reproduce the issue by following the given steps above.

After enabling "Title Bars", and selecting "UI Layout for the browser's top chrome" to "Refresh" in chrome://flags, the color of the top bar is Windows accent color, but cannot observe the line under the tabs as accent color.
Attached is the screen cast of the steps followed.

Request you to check and confirm if anything is missed form our end in triaging the issue.

Also request you to retry the issue on new chrome profile without any flags/extensions and update the thread with the observations.

Thanks..

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Hi,
Thanks for replying to me. 
I've tried myself again and figured out the problem.

Here's an updated "Steps to reproduce the problem":

1. Go to the Settings app on Windows 10. 
2. Go to Personalization/Colors. 
3. Go to "Show accent color on the following surfaces". 
4. Enable "Title Bars". 
5. Go back to the main page of the settings app.
6. Go to "System".
7. In the "display" section, find "Scale and Layout".
8. Select 150% scale.
9. Sign out of Windows and Sign in again.
10. Open Chrome Canary and go to "Chrome://flags"
11. Select "UI Layout for the browser's top chrome" to "Refresh".
12. Restart Chrome Canary
13. After restarting Chrome Canary and look at the top bar. 
14. Create a new tab and look at the top bar again. It looks really weird. 

PS: I scale the text and other elements on my computer because it has a very high resolution. 

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

nanjingchj@ Thanks for the update.

Able to reproduce this issue on Windows 10 on the reported version 69.0.3457.2 and the latest Canary 69.0.3469.3 as per comment #4.
Issue is not applicable to Ubuntu 14.04 and Mac OS 10.13.5.

Can observe the line under the tabs as accent color by setting #top-chrome-md flag to 'Refresh'.
This is a Non-Regression issue as this issue is observed from M-68 chrome builds from the introduction of #top-chrome-md flag
Attached is the screen cast for reference.

Hence marking this as Untriaged for further updates from Dev.

Thanks..

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	852899-1.mp4 2.6 MB View Download

I'm not sure if this is the same issue as described, but I'm also seeing odd rendering for the tabs when the Win10 color setting is set to show color in Title Bars.  Per the attached: you can see the vertical gray divider line appearing on the left side of the first pinned tab.  When the Win10 settings don't put color here the line is fine, since the background color is the same as the tab color.  But when it's another color (like blue, per the attached), the line is superfluous, and looks pretty weird.

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*** UI Mass Triage ***

 Unable to reproduce the issue, if this bug still reproduces for you, please reopen or file a new issue. Thanks!