Here is a tutorial (also by Lullah) on how to change the bootstrap colors to custom colors.

You can fix the credit by changing

<!------------- credit ------------->
  <div class="text-right"><a href="Lullah" class="tooltipster" title="code by Lullah"><i class="fas fa-paw"></i></a></div>
</div>

to 

<!------------- credit ------------->
  <div class="text-right"><a href="https://toyhou.se/Lullah" class="tooltipster" title="code by Lullah"><i class="fas fa-paw"></i></a></div>
</div>

Hope this helped!