Hi, you need to update the SCSSPHP compiler in the helixultimate plugin, currently you are using version 1.4.1 and it is not able to compile Bootstrap or SCSS like this.

$utilities-colors: map-merge(
  $theme-colors-rgb,
  (
    "black": to-rgb($black),
    "white": to-rgb($white),
    "body":  to-rgb($body-color)
  )
) !default;

The latest version is 1.6.0 which compiles correctly both bootstrap and other custom functions and mixins. I have tried it and you only need to update scssphp in plugin, I think many of us will appreciate it if you include it in the next version of helixultimate.

Thanks.