The user name in the order table does not have a css class based on user role, so you’ll need to add these.
You would do this in:
plugins/woocommerce/includes/admin/class-wc-admin-post-types.php (around line 742 for WC 2.6.14)
Extra code lines would be needed to determine the role of the user and add an appropriate css class.
Next, you’ll need some custom admin css to add colours to the classes.
The bigger problem though is that any edits to this file will be overwritten by WooCommerce updates, and these are quite regular. The file is not a template file, so no kind of protection from updates is available.
Good luck with that!