Your install screenshot looks very strange, almost as if you have a broken installation. Mods for HESK has a blue color scheme, while your screenshot looks like the "classic" HESK green. Make sure that you installed HESK first, and then properly installed Mods for HESK via the installation instructions at https://mods-for-hesk.mkochcs.com/download.php.
Also make sure to clear any server-side caches you may have enabled (such as Redis or CloudFlare)
Mike, Lead Developer of HESK: A surprisingly simple, user-friendly and FREE help desk software with integrated knowledgebase.
1. Redownload Mods for HESK at https://mods-for-hesk.mkochcs.com/download.php.
2. Extract the zip and copy+paste to your HESK install. Be sure to overwrite the Mods for HESK files over the HESK ones. (If you use a Mac, you may need to "merge" the folders. Windows will merge automatically)
3. Then go back to http://pathtoyourhelpdesk/install and see if the color scheme is fixed.
If you still have issues, open a confidential issue at https://gitlab.com/mike-koch/Mods-for-HESK/issues/new. Please include your helpdesk URL and FTP credentials so I can view the structure of your helpdesk installation.
Mike, Lead Developer of HESK: A surprisingly simple, user-friendly and FREE help desk software with integrated knowledgebase.