Below is the source code -
I can bold relationships(lines/arrows) between systems but not for the borders of the system. It will be a good feature to allow borders of the system, container, component, deployment node or node's border to be made bold or allow styling for the border line width.
@startuml banking-context title PoC for Architecture as Code 'LIBRARIES !include <C4/C4_Context> 'Border colors for systems AddElementTag("updatedSystem", $borderColor="orange" ) AddElementTag("newSystem", $borderColor="green") AddElementTag("existingSystem", $borderColor="red") 'Interactions - Updated, New, Emphasized AddRelTag("updatedInterface", $textColor="orange", $lineColor="orange", $lineStyle = DashedLine()) AddRelTag("newInterface", $textColor="green", $lineColor="green", $lineStyle = dotted) AddRelTag("EmphasizeInterface", $lineStyle = "boldLine") Person(customer, "Primary Customer") System(bankingApp, "Banking App", "Customer Bank Interface", $tags="existingSystem") Rel(customer, bankingApp, "Make Transaction") Rel(customer, bankingApp, "Update Profile", "http") Person_Ext(addOnCustomer, "Add On Customer") Rel(addOnCustomer, bankingApp, "Read Transaction", "https", $tags="EmphasizeInterface") System_Ext(email, "Email System", "Email Notification System", $tags="newSystem") Rel(bankingApp, email, "Post", "http", $tags="newInterface") System_Ext(las, "LAS", "Logging And Analytics System", $tags="updatedSystem") Rel(bankingApp, las, "Post", "http", $tags="updatedInterface") SHOW_LEGEND() @enduml