No, at least not me. The TsWorkbookTabControl is a standard TTabControl descendant which is drawn by the widgetset and therefore does not support colored tabs in general. Using a third-party tab control, such as ATTabs from ATFlatControls, would make it possible, though, but this would pull in the dependence on another library which I want to avoid. But nothing prevents you from doing this yourself in your application. Use ATTabs instead of TTabSheet and build its simple spreadsheet functionality yourself taking the code of TsWorkbookTabControl as a template.
One thing to be mentioned is that the current file reader/writers ignore the tab color in the files.