The horror from the ruins, how to get orange tickets?

During the event killing monsters in the world map will let you earn up to 100 'Shadow assassin chests' a day. Find these in your items bag under the Resources section.

'Use' these chests to exchange them for random rewards. Orange tickets are one of the possible rewards but they are rare.

You can also earn Skin Exchange vouchers as rewards. During the event you can use these in the Exchange Shop (found in the benefits center) and you can exchange for a limited number of Orange tickets here as well as other items.