How to change CocInlayHint colors?

[jonashaag]

Please excuse my naive question. I couldn't for the life of me figure out the right syntax to change the CocInlayHint colors. Here's what I have now, which has no effect:

return {
	{
		"projekt0n/github-nvim-theme",
		lazy = false, -- make sure we load this during startup if it is your main colorscheme
		priority = 1000, -- make sure to load this before all the other start plugins
		config = function()
			require("github-theme").setup({
				groups = {
					all = {
						CocInlayHint = { fg = '#ff0000', bg = '#0000ff' },
					}
				}
			})

			vim.cmd("colorscheme github_light_high_contrast")
		end,
	},
}