Vim MacOS, custom highlight group color keeps getting overwritten no matter what

My .vimrc is

syntax enable
function! MyHighlights()
    highlight PreProc ctermfg=9
    highlight Comment ctermfg=2
endfunction
"""""

In my .vim/after/plugin/myColors.tex I have a file with

call MyHighlights()

I can see in :vimscripts, that the file is being loaded correctly: it is the final file being loaded yet it’s not working. It does work if I call the function manually in the command, but nothing works otherwise. For filetypes where I have lsp installed, calling the function when lsp is installed does work, but any other event like BufEnter, VimEnter, all of it fails.

There is nothing else in my .vimrc or .vim/.