Here is the list of all the CSS available for Joli Table of contents.

You need to use them for theming whenever they exist.

--jtoc-background-color
--jtoc-body-background-color
--jtoc-body-margin
--jtoc-body-padding
--jtoc-close-button-background-color
--jtoc-close-button-color
--jtoc-column-color
--jtoc-column-gap
--jtoc-column-style
--jtoc-column-width
--jtoc-display
--jtoc-floating-active-heading-color
--jtoc-floating-max-width
--jtoc-floating-toc-current-heading-padding
--jtoc-floating-toc-offset-x
--jtoc-floating-toc-offset-y
--jtoc-floating-toc-shadow-color
--jtoc-floating-toc-z-index
--jtoc-floating-widget-background-color
--jtoc-floating-widget-border-radius
--jtoc-floating-widget-color
--jtoc-floating-widget-font-size
--jtoc-floating-widget-font-weight
--jtoc-floating-widget-height
--jtoc-floating-widget-nav-buttons-width
--jtoc-floating-widget-nav-color
--jtoc-floating-widget-numeration-color
--jtoc-font-size
--jtoc-header-background-color
--jtoc-header-border
--jtoc-header-border-radius
--jtoc-header-color
--jtoc-header-cursor
--jtoc-header-height
--jtoc-header-margin
--jtoc-header-padding
--jtoc-headings-background-color
--jtoc-headings-background-color-active
--jtoc-headings-background-color-hover
--jtoc-headings-border-radius
--jtoc-headings-color
--jtoc-headings-color-active
--jtoc-headings-color-hover
--jtoc-headings-font-size
--jtoc-headings-group-background-color
--jtoc-headings-line-height
--jtoc-headings-margin
--jtoc-headings-padding
--jtoc-hierarchy-offset
--jtoc-link-background-color
--jtoc-link-background-color-active
--jtoc-link-background-color-hover
--jtoc-link-color
--jtoc-link-color-active
--jtoc-link-color-hover
--jtoc-link-font-size
--jtoc-link-font-weight
--jtoc-link-margin
--jtoc-link-padding
--jtoc-max-width
--jtoc-min-width
--jtoc-numeration-color
--jtoc-numeration-color-active
--jtoc-numeration-color-hover
--jtoc-numeration-suffix
--jtoc-progress-bar-background-color
--jtoc-progress-bar-background-z-index
--jtoc-progress-bar-color
--jtoc-progress-bar-offset-y
--jtoc-progress-bar-thickness
--jtoc-progress-bar-z-index
--jtoc-slide-out-background-color
--jtoc-slide-out-padding
--jtoc-slide-out-toggle-background-color
--jtoc-slide-out-toggle-color
--jtoc-slide-out-toggle-offset-y
--jtoc-slide-out-width
--jtoc-title-color
--jtoc-title-color-alt
--jtoc-title-font-size
--jtoc-title-label-font-weight
--jtoc-toc-border
--jtoc-toc-border-color
--jtoc-toc-border-radius
--jtoc-toc-box-shadow
--jtoc-toc-margin
--jtoc-toc-padding
--jtoc-toc-root-margin
--jtoc-toggle-bg-color
--jtoc-toggle-bg-color-alt
--jtoc-toggle-border-color
--jtoc-toggle-border-color-alt
--jtoc-toggle-color
--jtoc-toggle-color-alt
--jtoc-width
--jtoc-z-index