php xlswriter 一个单元格的文本 可以指定某个字符有颜色吗？

可以的

$config = [
    'path' => '/tmp'
];
$excel = (new \Vtiful\Kernel\Excel($config))->fileName('tutorial01.xlsx', 'sheet1');

$redFormat = new \Vtiful\Kernel\Format($excel->getHandle());
$redStyle = $redFormat->fontColor(\Vtiful\Kernel\Format::COLOR_RED)->bold()->italic()->toResource();

$defaultFormat = new \Vtiful\Kernel\Format($excel->getHandle());
$defaultStyle = $defaultFormat->toResource();

$riches = []; // 创建富文本
$riches[] = new \Vtiful\Kernel\RichString("We", $defaultStyle);
$riches[] = new \Vtiful\Kernel\RichString(" are ", $defaultStyle);
$riches[] = new \Vtiful\Kernel\RichString(" 伐木累! ", $redStyle);

$filePath = $excel
    ->insertRichText(0, 0, $riches)
    ->output();

echo $filePath;