The 2014 SX had a yellow spring.

After feedback from owners, EBR decided that for the more upright riding position on the SX, they wanted to soften the spring slightly (red spring), so 2015+ had the red. There may be a few late 14s with the red spring, or early 15s with the yellow - I'm not sure that the change happened exactly at the same time as the production year build changed.

I bought a red spring from EBR and had it swapped onto my 14 - I honestly couldn't tell a difference in feel, but it matches my paint better, so I'm happy.