Looks like that blog assumes an init.vim configuration file. Lunarvim uses init.lua. You could have still used those same instructions to set it up.
Read this for more info: https://github.com/nanotee/nvim-lua-guide
Looks like the instructions in the readme works just fine: https://github.com/ChristianChiarulli/LunarVim#an-example-installation-of-the-colorizer-plugin which are more project specific than the blogpost.