[BUG] Highlighting configurations don't work

[BooleanCube]

Solution:

local hooks = require "ibl.hooks"
-- create the highlight groups in the highlight setup hook, so they are reset
-- every time the colorscheme changes
hooks.register(hooks.type.HIGHLIGHT_SETUP, function()
    vim.api.nvim_set_hl(0, "RainbowRed", { fg = "#E06C75" })
    vim.api.nvim_set_hl(0, "RainbowYellow", { fg = "#E5C07B" })
    vim.api.nvim_set_hl(0, "RainbowBlue", { fg = "#61AFEF" })
    vim.api.nvim_set_hl(0, "RainbowOrange", { fg = "#D19A66" })
    vim.api.nvim_set_hl(0, "RainbowGreen", { fg = "#98C379" })
    vim.api.nvim_set_hl(0, "RainbowViolet", { fg = "#C678DD" })
    vim.api.nvim_set_hl(0, "RainbowCyan", { fg = "#56B6C2" })
end)