Colours per row or column in the UI Toolkit table are set in its rendering events - the same technique as in questions 3130, 763 and 138:
// rows: Table > Events > On row rendered (row, record, index)
if (record.status === "OVERDUE") row.style.backgroundColor = "#f2dede";
if (index % 2 === 1) row.classList.add("striped-alt"); // zebra striping when the table style is off
// columns / cells: Column > Render cell (cell, record, column)
cell.style.color = record.amount < 0 ? "#a94442" : "#3c763d";
if (column.label === "Amount") cell.style.textAlign = "right";Whole columns without code: give the table a Custom CSS class and style the nth column: .myTable td:nth-child(3), .myTable th:nth-child(3) { background: #fcf8e3; } in a managed CSS asset. Refresh after data changes (${Table}.refresh()) so that the renderers run again. The old Dojo table (Coaches toolkit) only offered per-column style expressions; upgrade to the UI Toolkit table for anything data-driven.
References