Conclusion
HotXLS does not add ThemeColor / TintAndShade members to the classic lxHandle XLS facade. Those members belong to the newer OOXML style model and do not have a real, round-trippable BIFF .xls storage target. Adding them to the old XLS API would create a misleading surface: values would either be lost on save or reduced to an approximate palette colour.
The classic lxHandle XLS API writes BIFF .xls files. BIFF stores font, border, and fill colours through palette indexes, not Office theme colour slots.
Use Colour, ColorIndex, and Workbook.Colours
Use
Color when you want to assign an RGB value. HotXLS maps that RGB value to the current workbook palette. Use
ColorIndex when you want to address a palette slot directly. Use
IXLSWorkbook.Colours to customise palette entries.
Theme colours and tint/shade
ThemeColor and TintAndShade are OOXML .xlsx style concepts. The classic XLS facade does not expose those properties because a BIFF workbook has no equivalent theme/tint storage that Excel can round-trip as theme metadata.
If source code uses theme colours and the target file is .xls, resolve the theme/tint combination to an RGB colour first, then assign Color or a custom palette entry. If the theme relationship must remain editable in Excel, use the XLSX facade (lxHandleX) and its theme-aware style properties.
Example
This example customises a palette slot and uses it for a cell fill in a classic XLS workbook.
Workbook.Colors[8, 0] := RGB(42, 107, 191);
Workbook.Worksheets[1].Range['A1', 'D1'].Interior.ColorIndex := 8;