Also in Dark theme values in axes can't be viewed because text color like background color.

Also old graphs too:

Hello Evgeny,
Could you please provide us information on few basic questions:
1. Is this issue browser independent? Have you tried different one without any extensions or clean the browser cache? Please share us the browser version.
2. What is the distribution version and packages origin? Official Zabbix repo?
3. Do you use some http proxy?
We will replicate the issue and analyze.
Kind regards

Hello Michal,

1. Yes, I'm tried few different browsers and this problem is same for this.
   Chrome 110.0.5481.78
   Edge 110.0.1587.41
   Yandex Browser 23.1.2.931
2. Yes, latest version 6.2.7 from official repo.
3. No proxies.

Is it fresh 6.2.7 install or you have upgraded and if from what version? Please let us know also your host OS distribution and web server. We have to check exactly same packages. Please find the examples and let us know the details of your setup https://www.zabbix.com/download.
On screenshots you shared Dark theme colours looks like mixed with Blue. Please check the ownership of the fronted files. The workaround may be changing the of-work time itself so it is not even displayed but I understand it is far from satisfying.

This is fresh install of 6.2.7. As I understand all styles must be in CSS file \ui\assets\styles\dark-theme.css

In my case I'm modifyed this to corporate style and renamed CSS files...

BTW, "blue" theme is viewed normal, but dark theme seems have some hard-coded links

PS: zip-file is not supported to pushing here, if you want i can send it via mail (this file includes all changes by me for 6.2.7 version).

PS: in original style (dark-theme.css)  all OK

There is changes in dark CSS files:

# diff /usr/share/zabbix/assets/styles/dark-theme.css /usr/share/zabbix/assets/styles/x5tech_dark.css 
3111,3112c3111,3114
<   height: 30px;
<   background: url("../img/icon-sprite.svg?20220519") no-repeat 0 -864px; }
---
>   height: 50px;
>   background: url("../img/x5tech/x5tech_white.png") no-repeat;
>   background-size: 94px;
> }
3117c3119,3121
<   background: url("../img/icon-sprite.svg?20220519") no-repeat -570px -400px; }
---
>   background: url("../img/x5tech/x5tech_white.png") no-repeat;
>   background-size: 54px;
> }
3122c3126,3128
<   background: url("../img/icon-sprite.svg?20220519") no-repeat -540px -400px; }
---
>   background: url("../img/x5tech/x5tech_white.png") no-repeat;
>   background-size: 54px;
> } 

Also changing in /usr/share/zabbix/include/classes/core/ZBase.php from:

    public static function getThemes() {
        return [
            'blue-theme' => _('Blue'),
            'dark-theme' => _('Dark'),
            'hc-light' => _('High-contrast light'),
            'hc-dark' => _('High-contrast dark')
        ];
    } 

to:

        public static function getThemes() {
                return [
                        'x5tech_blue' => ('X5 Tech (Blue)'),
                        'x5tech_dark' => ('X5 Tech (Dark)')
                ];
        }
 

Also with all enabled themes:

With original theme:

This is not a bug nor problem with official code or packages. Please find the instruction how to add custom theme https://www.zabbix.com/documentation/current/en/manual/web_interface/theming. In current version you should target file /include/classes/core/APP.php. Regarding your changes in CSS files if you replacing .svg vector images they have to be exact same size and position. I would suggest to backup original files and edit the exact copy for your needs. If you want to replace the logo correctly please look upon this topic https://www.zabbix.com/documentation/current/en/manual/web_interface/rebranding.

Thanks Michal, I'm found my mistake in documentation:
 

Note: To change graph colors, the entry must be added in the graph_theme database table.

I am glad to hear your problems resolved. Thank you for confirmation Evgeny.