Error: Call to undefined function colors_create_css() in fullcalendar_page_attachments()

On a D8.82 site, when I enable Fullcalendar, it breaks the site with the error below. I followed the documentation to install the library. I initially installed v3.9 of the library. After getting the error, I tried v4.4 of the library but got the same results.

The website encountered an unexpected error. Please try again later.

Error: Call to undefined function colors_create_css() in fullcalendar_page_attachments() (line 200 of E:\Public_html\d8sandbox\web\modules\contrib\fullcalendar\fullcalendar.module)

#0 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(297): fullcalendar_page_attachments(Array)
#1 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(273): Drupal\Core\Render\MainContent\HtmlRenderer->invokePageAttachmentHooks(Array)
#2 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(117): Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\CurrentRouteMatch))
#3 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\EventSubscriber\MainContentViewSubscriber.php(90): Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\CurrentRouteMatch))
#4 [internal function]: Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object(Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent), 'kernel.view', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher))
#5 E:\Public_html\d8sandbox\web\core\lib\Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher.php(111): call_user_func(Array, Object(Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent), 'kernel.view', Object(Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher))
#6 E:\Public_html\d8sandbox\vendor\symfony\http-kernel\HttpKernel.php(156): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object(Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent))
#7 E:\Public_html\d8sandbox\vendor\symfony\http-kernel\HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#8 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\StackMiddleware\Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#9 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\StackMiddleware\KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#10 E:\Public_html\d8sandbox\web\core\modules\page_cache\src\StackMiddleware\PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#11 E:\Public_html\d8sandbox\web\core\modules\page_cache\src\StackMiddleware\PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#12 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\StackMiddleware\ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#13 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\StackMiddleware\NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#14 E:\Public_html\d8sandbox\vendor\stack\builder\src\Stack\StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#15 E:\Public_html\d8sandbox\web\core\lib\Drupal\Core\DrupalKernel.php(694): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#16 e:\public_html\d8sandbox\web\index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#17 {main}