I don't use zed or svelte, but this looks like the zed picture is missing a treesitter parser for svelte. Many editors have basic regex-based highlighting for many languages, and optional, more advanced, highlighting available through extensions. You may also get some semantic highlights provided by a language server if your editor uses the Language Server Protocol as well.
I found one extension from a web search. Did you try this? https://zed.dev/extensions/svelte