Changing Colors in Navigation Side Bar

How would I change the color of the light gray links in the navigation side bar? My url is

Hi @thuynh06,

I hope you are well today and thank you for your question.

You can try changing it by adding the following CSS code in the Custom CSS option of your theme on the below path.

Admin Area -> Apperance -> Theme Options -> Other -> Custom CSS

#secondary .widget_nav_menu a {
  color: #000 !important;

Please change the color value in the above code to whatever you want to use by referring the following pages.

Best Regards,