Humans and monsters exist together in peace then one day war breaks out. The humans win and the monsters are sealed underground and humans and animals exist in peace. One day. A hostile alien race called the Combine invade earth. They were so powerful that the humans lost this time. A human child named Frisk falls down mount. Ebbot to escape the Combine. Frisk gets a portal gun and befriend the monsters and break the barrior to stop the Combine once and for all
This is the colour of the portal gun in Portaltale Source.
This is not mine. All the credit goes to Branman10000. Its also going to be in the demo of the mod.