The bug

In previous versions (1.10 and maybe later) the beam which appeared when an entity teleported was yellow. In the latest versions it is always purple.

How to reproduce

1. Open Minecraft 1.10
2. Use the following command

   /setblock ~ ~ ~ end_gateway 0 replace {Age:201L}
   

3. Move inside the end gateway; the beam will be yellow
4. Open the latest Minecraft version
5. Use the following command

   /setblock ~ ~ ~ end_gateway default replace {Age:201L}
   

6. Move inside the end gateway
   → The beam will be purple instead of yellow