Reproduction steps:
1. Open project attached (Flicker.zip)
2. Open Scene "1".
3. Press play.

Expected result: Particles will have no effect to sprites colour.
Actual result: Sprites starts flickering.

Notes: This problem is easier to detect on 5.6 version, in 5.5 it is very hard to reproduce and any small changes might make this problem disappear (like turning off the arrows).
On ParticleSpawner there is script that instantiates particles and it seems to be the cause of this problem.
Directional light is optional and can be deleted from the scene.

Reproduced on: 5.5.0f3, 5.6.0a6, 5.6.0b3.
Not reproducible on: 5.5.0f1