Hello, @Kazi Sabit,
1- In order to solve your issue simply go to the Dashboard >> XStore >> Theme OPtions >> Theme Custom CSS >> Global and paste the below code at the bottom of the CSS box there.
#customer_details input{border-color:red !important;}
#customer_details .select2-container{border: solid 1px red !important;}
Then save settings and check back to your site after clearing the browser cache. The result will appear like this: https://postimg.cc/JtHy9994
Note: in the above code the word “red” is the color and you can change it with you want.
2- Thanks for your suggestion currently there is no option in the theme to make it as you describe. We will think about it.
Regards 8Themes Team.