Some guy on reddit claims to of received a solid red controller from a former Sega of America Employee...
"My friend used to work for sega. And she passed her Dreamcast collection on to me. A few years back. I joined the group right after. But haven’t seen anyone else post something similar."
First Thread of the Red Controller
https://www.reddit.com/r/dreamcast/comments/vg01f4/red_dreamcast_controller/
Updated Thread with pictures of the controller opened
https://www.reddit.com/r/dreamcast/comments/vizsv2/red_dreamcast_controller_pics/