To change the color of the mouse pointer, add the following css code to Appearance => Editor => Styles => Additional Css

@media screen and (min-width: 75em) {
.custom-cursor {
   background: red !important;
 }
}

Or you can change the primary color of the whole theme, which will change the color of the mouse pointer as well. For that go to Appearance => Editor => Styles => Colors => Edit Palette => Change primary color. Check the screenshots below:

Please let me know if this worked. Thank you.

Regards,
Sujeet