Yes it is possible to do that but as you mentioned it will require some CSS and code changes.

Can you provide me with admin access to your site so I can log in and make the changes?

To add me, in your Admin Dashboard, go to Users > Add New and use my email [email protected], make sure to assign me Administrator privileges.

To change the color of the green checkmark in the pricing tables you can use the following CSS code,

.pricing .pt_list .fas {
color: #12dabd;

Replace the color code with the one you wish.

Add this but of code in Appearance > Customize > Additional CSS.