Hello,

The Tasks have the ability to change their template as demonstrated here:

• https://demos.telerik.com/aspnet-ajax/gantt/examples/functionality/client-templates/defaultcs.aspx 

For small changes such as a color in a task, you can follow the suggestions in the first two points of the Improve Your Debugging Skills with Chrome DevTools blog post explaining how to inspect the generated HTML and check the applied styles for various elements. 

• Inspect the Generated HTML of a Control;
• See the Applied Styles;

Once you know the styles you need to override, you can use the same style selector and add "html body " in front of it to make it more specific, "stronger". More on CSS specificity you can find here: 

• Specifics on CSS Specificity;
• CSS Specificity: Things You Should Know;
• Specificity - CSS | MSDN;

For modifying the templates in the TreeList part, you can follow this feedback portal item:

• https://feedback.telerik.com/aspnet-ajax/1376053-gantt-treelist-column-template 

Regards,
Peter Milchev
Progress Telerik