@startuml !$successColour = "#00cc007f" !$failureColour = "#cc00007f" box Secure Participants participant Alice participant Bob end box participant Eve 'First case, with no background colour on the alt box alt When the conversation is secure Alice -> Bob: Sends message else $failureColour When the message is intercepted Alice -> Eve: Sends message end 'Second case, with a transparent blue background on the alt box alt $successColour When the conversation is secure Alice -> Bob: Sends message else $failureColour When the message is intercepted Alice -> Eve: Sends message end @enduml Submit amiga aws-orange black-knight bluegray blueprint cerulean-outline cerulean crt-amber crt-green cyborg-outline cyborg hacker lightgray mars materia-outline materia metal mimeograph minty plain reddress-darkblue reddress-darkgreen reddress-darkorange reddress-darkred reddress-lightblue reddress-lightgreen reddress-lightorange reddress-lightred sandstone silver sketchy-outline sketchy spacelab spacelab-white superhero-outline superhero toy united vibrant       🎉 Discover the future PlantUML Web Editor! 🚀  PNG  SVG  ASCII Art