Applied this diff:

@@ -284,7 +305,14 @@ require("lualine").setup({
     },
     -- TODO: indicator that LSP is working.
     lualine_c = { ls_status, "diagnostics" },
-    lualine_x = { "encoding", "fileformat", "filetype" },
+    lualine_x = {
+      "encoding",
+      "fileformat",
+      {
+        "filetype",
+        colored = true,
+      },
+    },
     lualine_z = { "%P" },
   },
 })

But no colours. Looks like colours rely on nvim-web-devicons, but I'm using vim-devicons, which uses different icons.