All of the three (maybe four) Robros a.k.a Shard, Cyber, and Metal are destined to have their eye color change after they change sides.
Shard's red eyes turned green,
Cyber's turned from navy to Crystal blue, but Metal hasn't gotten his yet.
It is theorized that they may be green like Sonic's and Shard's, or a cyan due to his gem being blue and having a strong connection with Sonic.