Reproduction steps:
1. Open the attached project "testParticles.zip";
2. Open the "demo scene";
3. Enter a play mode.

Expected results: as the start color is set to rainbow gradient and the sub-emitter should inherit the color of main particles, the ribbon trail should inherit the exact color of main particles.
Actual results: the ribbon trail inherits only one color from main particles and changes it randomly over the time.

Reproducible on: 2017.3.0b1, 2017.3.0b8, 2018.1.0a3.
(Trail mode only appears from 2017.3 beta)