Hi tumateix,
Thank you for your purchase.

You can apply the style for your columns and table by going to wpdatatable settings page and click on Color and Font settings tab. ( attachment ) 

You can also find some more information about that in our documentation.  

About the same column set:
As I understand you want to have same columns for all of your tables. Correct me if I am wrong.

If that is the case, if you are uploading the file ( using Add from data source option and I assume that file will have the same column names ) when you upload it you will have the same columns every time.

Hope this can help.
Best regards.

Hi tumateix,

Ok now I can see.
If your all tables have the same name of columns this can be done with some CSS inserting in the Custom CSS field in wpdatatables settings page.

If not maybe the best option is to change the color directly when you create table and choose the column colour from the column settings.
Otherwise it is not possible.

Best regards.

HI tumateix,

You will need to get the selector of the desired column and then use that selector when making the code in CSS.
But in your case ( because I can see that you have a lot of columns) my suggestion is to change the color directly for each table in the column settings like you did with the table in the link below to avoid any issues if the code is not right.

Best regards.