Rework themes for parity with the old nav
### Problem to solve We've received numerous requests about missing the theme options available in the old navigation. These themes served as a simple way to distinguish GitLab from other webpages, and without them it can be hard to swap between different instances. ### Proposal Each available theme should have a distinct visual representation in the new navigation. ![Default.png](/uploads/3e25d8a53e123b34e3393c2649780bfc/Default.png) ![Figmacon2.svg](https://gitlab.com/gitlab-org/gitlab/uploads/ea3b08ed66587abf3c90d0f64c19d068/Figmacon2.svg) [**View Figma →**](https://www.figma.com/file/jp4vmGJIlhSkvsy4JisduQ/%23378549-Rework-themes-for-parity-with-the-old-nav?type=design&node-id=122%3A86699&mode=design&t=7FTmyYyKV3Ywrohu-1) ### Implementation specs Each of the colored theme will use a similar scale of color variables. | Theme | Scale | Sidebar border color | |-------|-------|----------------------| | Gray | `$gray-900/100/50` | `$gray-950 8%` | | Indigo | `$t-indigo-900/100/50` | `$gray-950 8%` | | Light Indigo | `$t-indigo-700/100/50` | `$gray-950 8%` | | Blue | `$t-blue-900/100/50` | `$gray-950 8%` | | Light Blue | `$t-light-blue-700/100/50` | `$gray-950 8%` | | Green | `$t-green-900/100/50` | `$gray-950 8%` | | Light green | `$t-green-700/100/50` | `$gray-950 8%` | | Red | `$t-red-900/100/50` | `$gray-950 8%` | | Light Red | `$t-light-red-700/100/50` | `$gray-950 8%` | ### Data [Current theme usage](https://app.periscopedata.com/app/gitlab/695468/User-preferences-(90-day-active-users)?widget=10039861&udv=0) <details> <summary>Snapshot</summary> ![Screen_Shot_2022-11-16_at_9.42.49_AM](/uploads/819bfd1d0c45e350d1ec44beac0f0931/Screen_Shot_2022-11-16_at_9.42.49_AM.png) </details> ### What does success look like, and how can we measure that?
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