Custom highlighting of header in alpha starting screen plugin of nvim not working

I want to change the color of the header in alpha.nvim dashboard. I can set it to predefined highlight groups(right now "Error") but I want to provide a custom hl_group. I use vim.cmd(hi custom guifg="hex" guibg="hex" gui="none") before dashboard.section.header.opts.hl = 'custom' but it sometimes works and sometimes doesn't. This is inside a alpha.lua where

return {
  'goolord/alpha-nvim',
  dependencies = { 'nvim-tree/nvim-web-devicons', 'BlakeJC94/alpha-nvim-fortune' },
  config = function()
    local alpha = require("alpha")
    local dashboard = require("alpha.themes.dashboard")
    local fortune = require("alpha.fortune")

    math.randomseed(os.time())

    local ascii_arts = {}
    dashboard.section.header.val = ascii_arts['pacman']

    -- vim.cmd('hi custom <my values>')
    -- vim.cmd('hi custom')
    dashboard.section.header.opts.hl = "Error" -- custom
    dashboard.section.buttons.opts.hl = "Debug"
    dashboard.section.footer.opts.hl = "Conceal"
    dashboard.config.opts.noautocmd = true

    vim.cmd [[autocmd user alphaready echo 'ready']]

    alpha.setup(dashboard.opts)

also when I set dashboard.footer.opts.hl to "Custom" that also doesn't work. I tried to google it, ask on reddit but couldn't find any solutions. Most of trouble shooting I did was thanx to chatGPT. When I vim.cmd('hi custom') after I set custom then it shows the value that I want it to all the time. Highlighting works sometimes randomly. So when it doesn't I enter :hi custom in terminal and the result it xxx cleared so it's probably not working cuz nvim is not setting my custom highlight at the right time but I don't know how to fix it.

You can define bg & fg of the color groups "AlphaShortcut, AlphaHeader, AlphaHeaderLabel, AlphaButtons, AlphaFooter" in your colorscheme config.

Example using catppuccin colorscheme:

return {
  "catppuccin/nvim",
  config = function()
    require("catppuccin").setup({
      custom_highlights = function(colors)
        return {
          AlphaShortcut = { fg = colors.red, bg = colors.mauve },
          AlphaHeader = { fg = colors.red, bg = colors.mauve },
        }
      end,
    })
  end
}