expect color highlighting but there is no such a feature in my neovim

[icgoogo]

Describe the bug
no color highlighting in my neovim with coc-flutter plugin

To Reproduce
Steps to reproduce the behavior:
just type a color you want

Expected behavior
I expect to see color highlighting in my neovim but I didn't
how to activate color highlighting

Screenshots

Desktop (please complete the following information):

• OS: Macbook Ventura 13.0.1
• Neovim
• (Neo)vim version:
  NVIM v0.9.1
  Build type: Release
  LuaJIT 2.1.0-beta3

Config
I just copied all of the example config from coc plugin entirely
https://github.com/neoclide/coc.nvim#example-lua-configuration

[brainwo]

This extension and all the other coc.nvim extensions are only for language server.

If you need syntax highlighting, you can use https://github.com/dart-lang/dart-vim-plugin or use https://github.com/nvim-treesitter/nvim-treesitter to auto download syntax highlighting.