Hello and thank you for contacting Infragistics. Our API (linked below) can be styled in CSS using lower-case property names based on the component it belongs to. IgrDataGrid > ig-data-grid

www.infragistics.com/.../igrdatagrid.html

eg. The column options and toolbar are separate components that need to be styled as such:

.ig-grid-column-options {
--background-color: #191919;
--text-color: #7446b9;
}

.ig-data-grid-toolbar {
--background-color: #191919;
--text-color: #7446b9;
}

Here is a template and sample from our Grid portion in Dark.

eg. codesandbox.io/.../hardcore-almeida-suxfxn

.ig-data-grid {
/* shared variables used in custom properties */
--grid_selected_background: #58258b;
--grid_selected_text_color: #ffffff;
--grid_normal_background: #191919;
--grid_normal_text_color: #cccccc;
--grid_section_background: #333333;
--grid_section_text_color: #cccccc;
--grid_focused_color: #7446b9;
--grid_hyperlink_text_color: #926ec7;
--grid_error_text_color: #c62828;
--grid_hover_background: #777777;
--grid_icon_color: #333333;
--grid_lines: #272727;

/* root summary */
--summary-root-background: #7446b9;
--summary-root-label-text-color: #191919;
--summary-root-value-text-color: #191919;

background-color: var(--grid_normal_background);

--row-separator-background: var(--grid_lines);
--row-separator-last-sticky-row-background: var(--grid_lines);
--row-separator-pinned-row-background: var(--grid_focused_color);
--row-separator-sticky-row-background: var(--grid_focused_color);

--header-background: var(--grid_normal_background);
--header-text-color: var(--grid_normal_text_color);
--header-separator-background: var(--grid_lines);
--header-separator-width: 5px;

--section-header-background: var(--grid_section_background);
--section-header-text-color: var(--grid_section_text_color);
--section-header-selected-background: var(--grid_selected_background);
--section-header-selected-text-color: var(--grid_selected_text_color);

--cell-selected-background: var(--grid_selected_background);
--cell-selected-text-color: var(--grid_selected_text_color);

--cell-text-color: var(--grid_normal_text_color);
--cell-background: var(--grid_normal_background);

--sticky-row-background: var(--grid_color_focused);
--last-sticky-row-background: var(--grid_color_focused);

--pinned-row-background: var(--grid_color_focused);
--pinned-row-opacity: 0.5;

/* not working column properties */
/* --default-column-width: 150; */
/* --default-column-min-width: 20; */

--column-resizing-separator-background: var(--grid_focused_color);
--column-moving-separator-background: var(--grid_focused_color);
}

Hello and thank you for following up. I've created a bug internally to address this issue. I've switched this forum over to a private case. C-00227938, and you can access it after signing into your account on the Infragistics website, here: account.infragistics.com/support-cases.