This only happen if you are the client. There are several weapons like the recent Opticor Vandal, the Redeemer Prime, and the Gram Prime are some that have been tested in the field. They display a different energy color after every shot or swing.
The Opticor Vandal has the default energy color of its blast fx as shown below. The Redeemer Prime's wave is the default color. The worst offender is the Gram Prime. The fx was blinding the whole screen and it's really uncomfortable.
This is dozens of effects that are hit with this bug, maybe a hundred. Just from the top of my head: Zenurik's lightning dash's lightnings, Helios' eye, Baruuk' Desert Wind fists, Simulor's and Larkspur's explosions are half blue as well, etc, etc...